N. High-performance Lead-free Piezoelectric Ceramics

Organizers: Jing-Feng Li, Satoshi Wada, Jae-Ho Jeon, Jae-Shin Lee

N-01(Invited) Preparation of BNT-BT Grain-Oriented Ceramics and Their Piezoelectric Enhancement by Domain Enginnering Satoshi Wada, Ryo Ito, Minsu Kim, Shintaro Ueno, Nobuhiro Kumada University of Yamanashi The engineered domain technique is one of the well-known domain engineering techniques for piezoelectric enhancement, which is composed of two parts, (1) domain wall fixing technique on the basis of crystallographic anisotropy and (2) increasing domain wall density on the basis of grain size control. This is because domain wall itself is very soft and possess very high dielectric and piezoelectric properties. For tetragonal perovskite oxide materials, crystallographic directions are <111> and <110> directions to fix domain walls into the materials. We previously reported the preparation of the <111> oriented barium titanate (BaTiO3, BT) ceramics using by electrophoresis deposition (EPD) method under high magnetic field (HM-EPD) of 12 T, and piezoelectric enhancement with d33 of 500pm/V. On the other hand, we also reported the preparation of the <110> oriented BT ceramics using by template grain growth (TGG) method, and piezoelectric enhancement with d33 of 800pm/V. However, the Curie temperature (TC) of BT is 132oC, and this is very low for the most of piezoelectric applications, which need the higher TC over 200oC. Thus, in this study, we focus bismuth sodium titanate ((Bi0.5Na0.5)TiO3, BNT)-BT (BNT-BT) system ceramics with high TC of around 250oC. Using tetragonal 0.85BNT-0.15BT chemical compositions, two kind of grain-oriented ceramics along <111> and <110> directions were prepared by different methods as reported for BT grain-oriented ceramics. These details will be presented at conference. N-02(Invited) Quenching Effects for Electrical Properties on Lead-Free (Bi1/2Na1/2)TiO3-Based Ceramics Hajime Nagata, Hiroki Muramatsu, Tadashi Takenaka Tokyo University of Science Lead-free ferroelectric and piezoelectric ceramics, (Bi0.5Na0.5)TiO3 (BNT)-based ceramics, were fabricated by a quenching procedure during a sintering process, and then electrical properties for these BNT-based ceramics were investigated aiming to increase the depolarization temperature Td of BNT-based ceramic. From the measurement of temperature dependences of dielectric properties on BNT ceramic, the Td increased with increasing the quench temperature. The Td value of quenched BNT sample at 1100oC was 223oC, which was almost 50oC higher than that prepared by the ordinary cooling process. From the measurement of P-E hysteresis loops, both remanent polarization Pr and coercive field Ec were almost the same between two BNT samples prepared by ordinary firing and quenched at 1100oC. Additionally, from the measurement of resonance and antiresonance method, an electromechanical coupling factor k33 of ordinary fired BNT was 0.45, and that of quenched one was 0.46. From these results, it is clarified that quenching procedure is effective way for increasing Td of BNT ceramic without decrease of ferroelectric and piezoelectric properties. N-03(Invited)

Comparable Studies on High- and Low-Signal Mechanical Properties of (Bi1/2Na1/2)TiO3-SrTiO3 Ceramics Seung Ho Han1, Sora Jo1,2, Chang-Hyo Hong3, Chang Won Ahn4, Hyung-Won Kang1, Hyeung-Gyu Lee1, Sahn Nahm2, Wook Jo3 1. Korea Electronics Technology Institute 2. Korea University 3. Ulsan National Institute of Science and Technology 4. University of Ulsan

A high normalized strain (Smax/Emax) at high electric fields were reported in various (Bi1/2Na1/2)TiO3(BNT)-based ceramics. In particular, (1-x)BNT-xSrTiO3(ST) ceramics in the composition near x = 0.25 (25ST) have high normalized strain of ~0.45% due to the electric-field-induced phase transition. Although there have been many reports on the high strain behaviors of BNT-based ceramics, their mechanical properties have not been reported, yet. In addition, because the strains at high- and low- electric field of BNT-based ceramics are thoroughly different, the mechanical properties of BNT-based ceramics at high electric field should be addressed. In this work, we report the mechanical properties of the (1-x)BNT-xST ceramics in the composition range of 0 ≤ x ≤ 0.25. To evaluate the low-signal (~1V) mechanical properties, we measured the resonance/antiresonance frequencies of four different vibration modes samples (length, shear, thickness, and radial), and subsequently extracted various tensors of compliances based on JEITA EM-4501 (Electrical test methods for piezoelectric ceramic vibrators). The mechanical properties at high-signal (1-4kV/mm) were extracted from stress-strain curve with applying high electric field using BNT-ST multilayer device. We investigated the correlation between high- and low-signal induced mechanical properties of BNT-ST ceramics.

N-04(Invited) Large Strain in Textured Bi0.5(Na,K)0.5TiO3-Based Relaxor/Ferroelectric Composite Ceramics Chang Won Ahn1, Ill Won Kim1, Jae-Shin Lee1, Wook Jo2 1. University of Ulsan 2. UNIST

Textured (1-x)(Bi0.5(Na0.78K0.22)0.5TiO3)-xBiAlO3 (BNKT-BA-x; x=0, 0.03) ceramics were fabricated by reactive templated grain growth (RTGG) method with the viewpoint of improving the strain response and reducing the driving electric field from grain orientation. In addition, to more improved electric-field-induced strain properties of textured BNKT-based ceramics at lower electric field, we have fabricated relaxor/ferroelectric composite structured ceramics. BNKT-BA-0 and BNKT-BA-0.03 ceramics were used as ferroelectric layer and relaxor layer, respectively. The textured ceramics show high orientation factor (lotgering’s factor) >90%. The textured BNKT-BA-0.03 ceramics exhibited large strain (S = 0.47%) at applied electric field of 45 kV/cm, which corresponds to a normalized strain (Smax/Emax) of ~1040 pm/V. This normalized strain value is 75% larger than that of non-textured BNKT-BA-0.03 ceramics. Furthermore, the relaxor/ferroelectric composite ceramics showed very large normalized strain value of 1340 pm/V at relatively lower electric field of 35 kV/cm. This research was supported under the framework of international cooperation program managed by National Research Foundation of Korea (NRF-2014K2A2A2000609) N-05 Enhanced Piezoresponse and Electric Field Induced Relaxor-to-Ferroelectric Transition in NBT-0.06BT Ceramic Prepared from Hydrothermally Synthesized Nanoparticles

Xuefan Zhou, Chao Jiang, Chao Chen, Hang Luo, Kechao Zhou, Dou Zhang State key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China In this study, 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-0.06BT) nanoparticles were synthesized by the hydrothermal method and subsequently were used to prepare NBT-0.06BT ceramic. The effects of polarization on crystalline phase, microstructures, dielectric properties and domain structures of the ceramics were investigated in detail to reveal the origin of enhanced piezoresponse and large electric field induced strain in as-prepared NBT-0.06BT ceramic. The crystalline phases of NBT-0.06BT nanoparticles and ceramic were tested by X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) images of the ceramic were taken with a JEM-2100F transmission electron microscope. A precision impedance analyzer (4294A, Agilent, PaloAlto, CA) was used to obtain the variation of dielectric constant and loss tangent as a function of frequency and temperature. The ferroelectric hysteresis loops and field-induced strain curve were obtained by using a typical Sawyer-Tower configuration and an inductive nanopositioner linear variable differential transformer (LVDT) sensor. Polarization was performed in silicone oil at 80 °C for 15 min under an electric field of 3.5 kV/mm. The piezoelectric charge coefficient, d33, was measured 24 h after polarization using a Berlincourt d33 meter (APC). Planar electromechanical coupling coefficient (κp) was calculated by resonance and anti-resonance technique using impedance analyzer. The ceramic was polished for investigating domain structures by the piezoresponse force microscopy (PFM) mode of an atomic force microscope (NanoManTM VS) with a conductive Pt/Ir-coated Si cantilever (SCM-PIT). The domain structures were obtained by keeping the Pt-coated tip fixed on the surface and appling an ac voltage with amplitude Vac= 10 V and frequency f= 41 kHz. The XRD results of unpoled and poled NBT-0.06BT ceramics suggested the rhombohedral- tetragonal morphotropic phase boundary (MPB) existed in as-prepared ceramics and tetragonal phase in the ceramics was enhanced after polarization. After poling at an electric field 3.5 kV/mm, the piezoelectric coefficient (d33) and electromechanical coupling factor (κp) reached 171 pC/N and 0.31, respectively. The NBT-0.06BT ceramic exhibited a large remanent polarization of 46.10 μC/cm2 and electric field induced strain of 0.243% at 8 kV/mm with normalized strain d33*=303 pC/N (Smax/Emax). It can be observed that the polar nanoregions (PNRs) were transformed into lamellar domains after polarization. The dielectric response of NBT-0.06BT ceramic also exhibited an electric-field-induced relaxor-to-ferroelectric phase transformation. In summary, NBT-0.06BT nanoparticles were synthesized by a hydrothermal method. The corresponding NBT-0.06BT ceramic possessed enhanced piezoelectric response and large electric-field-induced strain. The origin of large piezoresponse and strain of NBT-0.06BT ceramic was attributed to the coexistence of ferroelectric phase and relaxor phase under unpoled state along with domain switching and field-induced relaxor-to-ferroelectric phase transition when applying an electric field. N-06(Invited) Core Shell Domain Structure and Electric Field Induced Strain of 0.77Bi0.5Na0.5TiO3-0.23SrTiO3 Ceramics Jeong-Ho Cho, Jung-Soo Park, Seong-Won Kim, Woon-Ik Park, Ji-Sun Yun, Young-Hoon Jeong, Jong-Hoo Paik KICET Method: 0.77Bi0.5Na0.5Ti1-xFexO3-0.23SrTiO3 ceramics (0≤x≤0.04) (BNTF-ST) were prepared by using a conventional solid-state reaction method. The microstructure and domain morphology of BNTF-ST ceramics were investigated with field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM).

Result: From the TEM observation, the domains with strip morphology were transformed to nanodomains with increasing Fe content x. For the specimens with x=0.04, approximately 30% of the grains showed a core-shell structure. The R3c perovskite structure was characterized by the presence of 1/2(ooo) super-lattice diffraction spots along the [011] zone axis and the absence of 1/2(ooe) spots along the [111] zone axis for all compositions. As the Fe content x was increased, the remnant polarization and the coercive field were decreased indicating ferroelectric to non-polar phase transition. For the composition of x=0.04, the enhanced normalized strain of 550 pm/V was obtained by core shell structure under an applied electric field of 2 kV/mm. N-07(Invited) Effect of BiMeO3 on the Phase Structure, Ferroelectric Stability, and Properties of Lead-Free BNT-Based Piezoelectric Ceramics Jiwei Zhai, Jigong Hao Functional Materials Research Laboratory, School of Materials Science & Engineering, Tongji University, No. 4800 Caoan Highway, Shanghai 201804, China The effects of perovskite type Bi-based ferroelectrics BiMeO3 (Me = Fe、Sc、Mn、Al) on the phase transition structure and electrical properties of BNKT20 ceramics were systematically studied. Results showed that BiFeO3 (BF) addition induced the phase structure of the ceramics changing from coexistence of rhombohedral and tetragonal to a single tetragonal phase, and promoted the piezoelectric properties of the ceramics (at 2mol%BF, d33 reached up to 150pC/N). While a small amount of BiScO3 (BS), BiMnO3 (BM) and BiAlO3 (BA) substitutions resulted in a transition from coexistence of rhombohedral and tetragonal to pseudocubic symmetry with relaxor characteristics, leading to degradations of the ferroelectric properties. Moreover, these substitutions led to the formation of the ergodic relaxor phase and significantly enhanced the strain response of the ceramics (2.75mol%BS, d33*~438pm/V; 2.25mol%BM, d33*~446pm/V; 1.75mol%BA, d33*~423pm/V). Furthermore, we found BNKT20-BiMeO3 systems achieved their maximum d33* values in the vicinity of ferroelectric-ergodic relaxor phase boundary, and the position of ferroelectric-ergodic relaxor phase boundary shifted to a BNKT20-rich side with the increasing tolerance factor t of the end member from BS to BA. In addition, electric-field poling treatment shifted the TF-R to higher temperature, which suggested that the temperature range of ferroelectric behavior was extended by poling treatment. N-08(Invited) Synthesis of 0.93Na0.5Bi0.5TiO3-0.07BaTiO3 Platelets for Texturing and Energy Storage Applications Dou Zhang, Kechao Zhou Central South University Two-dimensional single crystalline perovskite 0.93Na0.5Bi0.5TiO3-0.07BaTiO3 (NBT-7BT) platelets with a morphotropic phase boundary (MPB) were synthesized by the topochemical technique, using bismuth layer-structured Na0.5Bi4.5Ti4O15 (NBIT) platelets as the precursor. Both NBIT and NBT-7BT platelets showed high aspect ratios with an average size of 10 μm and thickness of 0.6 μm. A structural transformation from bismuth layer-structured NBIT to perovskite NBT-7BT was identified. The poling behaviors of NBT-7BT platelets were measured. The piezoresponse amplitude for a NBT-7BT platelet indicated a large piezoresponse strain, corresponding to a field-induced Smax/Emax of as high as 800 pm/V. The single-crystalline NBT-7BT platelets were used as templates to prepare grain oriented lead-free NBT-7BT ceramics. The grain oriented NBT-7BT ceramic which was textured with 10 wt % of NBT-7BT templates and

processed at 1175 °C for 50 h exhibited a very high degree of grain orientation and a large Lotgering Factor of 0.89. The grain oriented NBT-7BT ceramic showed an excellent actuating performance of up to 0.7 % free strain at 7 kV/mm at room temperature, where the value of field-induced Smax/Emax was calculated to reach as high as 1000 pm/V. The single-crystalline NBT-7BT platelets were also used as fillers in poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix to prepare dielectric composites, after being pre-coated by polyvinylprrolidone (PVP). Together with a modified sandwich structures, NBT-7BT/P(VDF-HFP) composites showed breakdown strength of 215 kV·mm-1 and energy storage density of as high as 14.5 J·cm-3. N-09 Structural, Photoluminescence, and Electrical Properties of Er-Doped Na0.5Bi4.5Ti4O15 Lead-Free Ceramics Chao Chen, Xingan Jiang, Yalin Jiang, Xiang Xia, Xiangping Jiang Jingdezhen Ceramic Institute Structural, up-conversion (UC) and electrical properties of Na0.5Bi4.5-xErxTi4O15 (NBT-xEr3+) (0.00<x<0.40) ceramics have been studied. All NBT-xEr3+ compounds crystallized into an orthorhombic layered perovskite structure with a slightly decreased cell volume and orthorhombic distortion. The unit cell volume, the lattice parameters and orthorhombic distortion analyzed on the basis of Rietveld refinement were observed to decrease with increasing Er3+ contents (x). The average values of grain size were found to slightly decrease with increasing x. Raman spectroscopy indicated that Er3+ was not entering into the (Bi2O2)2+ layers, but into the A sites of pseudoperovskite layer. NBT-xEr3+ ceramic with x=0.20 achieved the optimized photoluminescence. The relative intensity of green and red UC emissions could be tuned by changing Er3+ ions concentrations. The incorporation of Er3+ ions increased the Tc with simultaneously lowered tanδ, making this ceramics suitable for piezoelectric sensor devices at higher temperature. Piezoelectric constant d33 was also slightly improved. Therefore, the NBT-xEr3+ ceramic samples could be considered as promising candidates for multifunctional optoelectronic sensor applications. N-10 Improved Piezoelectric and Luminescence Properties of Sm3+ Doped (Na1/2Bi1/2)TiO3 Based Lead-Free Multifunctional Ceramics Xiang Xia, Xiangping Jiang, Chao Chen, Yuhan Luo, Yalin Jiang, Sheng Zhu Jingdezhen Ceramic Institute

As a lead-free multifunctional material, ferro/piezoelectric ceramic doped with rare earth ions has attracted extensive attraction in recent years because of their potential applied value in optical-electrical multifunctional devices. In this work, we reported a high efficient orange-red emission with good piezoelectric properties based on 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3-xSm3+ (NBBT-xSm) ceramics. The samples with different amount of Sm3+ addition were prepared by a conventional solid-state reaction method. The crystal structure, electrical properties and photoluminescence performances of the samples were systematically investigated. It was found that doping Sm3+ into NBBT induced a transition from the coexistence of rhombohedral and tetragonal phases to a pseudocubic phase. The result of microscopic images reveled that all the samples possessed a well-sintered and compact microstructure and the addition of Sm3+ inhibited the grain growth of NBBT-xSm samples. With increasing Sm3+ doping content from x=0 to x=0.018, both dielectric constant and dielectric loss were decreased from 6524 and 0.072 to 3297 and 0.056 (measured at 100kHz), respectively. The sample with x=0.003 displayed a

relatively large piezoelectric constant (d33~202pC/N), indicating that a small amount of Sm3+ doping significantly improved the piezoelectric performance for NBBT ceramics. In addition, the obtained Sm3+-doped NBBT ceramics exhibited the strongest absorption peak located at 407nm corresponding to the transition from the 6H5/2 ground state to 4F7/2 excited state of Sm3+, which matches well with the emission wavelength of the commercial near-ultraviolet LED chips. Under the excitation of 407nm n-UV light, the samples presented characteristic emission of Sm3+ ions with the dominate orange-red emission peak at 598nm relating to the 4G5/2→6H7/2 level transition. Particularly, the quantum yield as high as 44% was achieved in the NBBT-0.006Sm specimen, which is higher than that of most of currently reported rare earth doped ferro/piezoelectric ceramics. Furthermore, the thermal stability of photoluminescence for the sample was studied in detail and the value of the thermal quenching active energy was calculated to be 0.5543eV. Our experimental results indicate that NBBT-xSm materials have promising potential in white light emitting diodes (WLEDs) or advanced multifunctional devices.

N-11(Invited) Resistive Switching Memory Integrated with Nanogenerator for Self-Powered Bio-Implantable Devices Sahn Nahm Korea University Resistive random access memory (ReRAM) devices powered by piezoelectric nanogenerators (NGs) have been investigated for their application to future implantable biomedical devices. Biocompatible (Na0.5K0.5)NbO3 (NKN) films that are grown at 300°C on TiN/SiO2/Si and flexible TiN/Polyimide (TiN-PI) substrates are used for ReRAM and NGs, respectively. These NKN films have an amorphous phase containing NKN nanocrystals with a size of 5.0 nm. NKN ReRAM devices exhibit typical bipolar switching behavior that can be explained by the formation and rupture of oxygen-vacancy filaments. They have good ReRAM properties such as a large ratio of RHRS to RLRS as well as high reliability. The NKN film grown on flexible TiN-PI substrate exhibits a high piezoelectric strain constant of 50 pm/V. The NKN NG has a large open-circuit output voltage of 2.0 V and a short-circuit output current of 40 nA, which are sufficient to drive NKN ReRAM devices. Stable switching properties with a large ON/OFF ratio of 102 are obtained from NKN ReRAM driven by NKN NG. N-12(Invited) Vertical Morphotropic Phase Boundaries (MPBs) in Lead-Free Piezoceramic Systems Tomoaki Karaki, Miao Yan, Shinki Ishitate, Tadashi Fujii, Masatoshi Adachi Toyama Prefectural University Objectives: It is well known that piezoceramics with a composition near the tetragonal-rhombohedral morphotropic phase boundary (MPB) have good dielectric and piezoelectric properties. The so-called vertical MPB means that the slope is perpendicular to the composition axis, and implies the temperature-stability of the piezoelectric properties in a wide temperature range, such as Pb(Zr,Ti)O3 (PZT). It is very important to search for vertical MPB composition in lead-free piezoceramic systems, so that then excellent piezoelectric properties could be expected. In this work, we successfully found some vertical MPBs in (K,Na,Li)NbO3-based lead-free piezoceramic systems. Methods: Carbonate and oxide powders were used as raw materials. After calcination at 1050 oC in air for 2 h and sintered at 1190 oC for 4 h in a sealed alumina crucible. The samples were crushed as powders for X-ray diffraction (XRD) analysis. The powder specimens were measured by XRD in 2θ=20-60o at room temperature (RT) to confirm their perovskite structure and MPB at RT. The Curie temperature Tc was determined from

temperature dependence of dielectric constant at 1 kHz. The (200)pc reflection of selected specimens were measured by XRD from RT to 400oC for phase transition determination. Results: From the high-temperature XRD analysis results there 3 vertical MPB compositions were discovered. One is 0.075BaZrO3-0.915(K0.45Na0.5Li0.05)NbO3-0.01(Bi,Na)TiO3 with a Tc of about 270oC. The second one is 0.09BaZrO3-0.9025(K0.45Na0.5Li0.05)NbO3-0.0075(La,Na)TiO3 with a Tc of about 195oC. Another one had a Tc of about 365oC. Conclusions: We successfully artificially formed vertical MPBs through adjusting MPB slope in lead-free piezoceramic systems. The results and research way in this work have important practical implications in addition to the scientific interest for searching high-performance lead-free piezocermics. Those lead-free systems could be used to develop high-performance lead-free piezoceramics compatible with lead-based PZT. N-13(Invited) Fabrication of (K,Na)NbO3 Epitaxial Films and Observation of the Domain Structures by Confocal Laser Scanning Microscopy Ichiro Fujii, Takahiro Wada Ryukoku University

Objective: (K,Na)NbO3 is the promising lead-free piezoelectric materials, and a successful device operation using a (K,Na)NbO3 polycrystalline film has been recently demonstrated. Therefore, the understanding of basic information on the crystal structures and electric properties of (K,Na)NbO3 epitaxial films with systematically varied K and Na contents is important. However, reports on such a study are limited. In this study, 1-3-μm thick (KxNa1-x)NbO3 films were grown on SrRuO3/(001)SrTiO3 substrates by pulsed laser deposition, and the properties were characterized. Methods: The (KxNa1-x)NbO3 films were formed by pulsed laser deposition. The crystal structures were analyzed by reciprocal space mapping. The polarization-electric field loops were measured by a ferroelectric tester. Domains were observed by confocal laser scanning microscopy. Results: Reciprocal space mapping of the films revealed that the films were epitaxially grown, and the crystal system was altered with increasing K content. Ferroelectric polarization - electric field loops were observed for the films, with the maximum remanent polarization of ~40 μC/cm2 at x=0.34. To understand this composition dependence of remanent polarization, domain structures of the (KxNa1-x)NbO3 films (x=0-0.30) before and after an electric field was applied were observed by confocal laser scanning microscopy. It was found that the number of domains with out-of-plane polarization directions increased with x. Conclusions: The remanent polarization was maximized at x=0.34 for the (KxNa1-x)NbO3 epitaxial films. This was attributed to increase in the number of domains with out-of-plane polarization directions. N-14(Invited) Physical Origin for High Piezoelectricity in KNN-Based Ceramics Jiagang Wu Sichuan University Potassium-sodium niobate [(K, Na)NbO3, KNN] is attractive as a potential lead-free piezoelectric material due to its comprehensively excellent electrical properties and lead-free characteristics. In the past several years, we have achieved a breakthrough in piezoelectricity (d33=426~490 pC/N) in KNN-based ceramics by composition modification and phase boundary construction [Chem. Rev., 2015, 115(7), 2559 and J. Am. Chem. Soc., 2014,

136(7), 2905]. However, the physical origin for its high piezoelectricity is still unclear. Here we systematically explored the physical mechanism for the enhanced piezoelectric performance by the measurement of transmission electron microscopy (TEM), piezoelectric force microscopy (PFM), In situ synchrotron X-ray diffraction, and so on. The structural origin of the high piezoelectric performance can be attributed to its nanodomain structure. The local structure inside nanodomains is the coexistence of rhombohedral and tetragonal nanotwins. Therefore, the physical origin of high piezoelectric performance can be attributed to low domain wall energy and nearly vanishing polarization anisotropy, which facilitates easily polarization rotation between different states and leads to high properties. N-15(Invited) High Qm Values and Humidity Effect on the Electrical Properties of (K, Na)NbO3 Lead-Free Piezoceramics Doped with B2O3-CuO Mixed Oxides Yuhua Zhen1, Linling Li1, Ke Wang2 1. College of Science, China University of Petroleum, Qingdao 266580, Shandong, P. R China 2. College of Materials Science and Engineering, Tsinghua University, 100084, Beijing, P.R China

To greatly enhance the mechanical quality factor (Qm) of piezoceramic materials, B2O3-CuO mixed oxides were added to a K0.48Na0.52NbO3-based lead-free piezoceramic (abbreviated as BC-KNN) and studied. The results suggest that the B2O3-CuO additives effectively improved the sinterability and Qm value of the piezoceramic. An optimal Qm value as high as 2128 was obtained, which is 35 times higher than that of pure KNN ceramics. Interestingly, we found that the Qm value was sensitive to humidity in the surrounding environment. As the relative humidity (RH) increased from 25% RH to 78% RH, the Qm value of the BC-KNN ceramics decreased from 2128 to 267. We found that the dependence of the Qm value on humidity was closely related to the instability of the capacitance (Co) and the relative dielectric constant (r). Our results show that a dense microstructure is critical for maintaining a stable high Qm performance in a humid environment. N-16(Invited) Local Piezoelectric Properties and Relaxation Behavior of (K,Na)NbO3-Based Piezoceramics with Abnormal Grain Growth Ke Wang, Tian-Lu Men, Wei Sun, Jing-Feng Li State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China During the past decades, lead-free piezoceramics has been developing extremely fast, due to the increasing concern on environmental protection. However, much attention has been paid to macroscopic property enhancement, which is usually conducted through compositional optimization and processing control. It is considered that further understanding on the microscopic level is necessary for further increasing the performance of lead-free piezoceramics. The present study is focused on the local piezoelectric response and relaxation behavior of a CaZrO3-modified (K,Na)NbO3 (KNN) ceramic sample, which is deliberately chosen due to its high macroscopic d33 more than 300 pC/N and the obvious abnormal grain growth microstructure. The experiments were accomplished by the multiple functions of the Piezoresponce Force Microscope (PFM), such as switching spectroscopy and lithography. It is shown that the different inner parts of one single large grain (around 5 μm) share a similar relaxation speed, while the parts from adjacent grains could vary widely even they share the same grain boundaries. By contrast, a

trend of diffused relaxation behavior is found for small grains (< 1 μm). Moreover, local piezoelectric measurement was performed on different areas, while the results indicate that large grain size could benefit local piezoelectric performance. It is considered that the macroscopic piezoelectric properties of KNN-based lead-free ceramics could be largely improved if samples with improved microstructure could be synthesized. N-17 Novel Morphotropic NaNbO3-BaTiO3-CaZrO3 Lead-Free Piezoceramics Jian Fu, He Qi, Ruzhong Zuo Hefei University of Technology Lead-free piezoelectric materials with a compositionally driven morphotropic phase boundary (MPB) separating ferroelectric tetragonal (T) phase from ferroelectric rhombohedral (R) phase have attracted extensive attention in recent years. In the present study, a novel NaNbO3-based lead-free ceramic was introduced to have temperature -insensitive piezoelectric and electromechanical properties (d33=231 pC/N, kp=35% and low-hysteresis strain ~0.15%) in a relatively wide temperature range. In this system, the T-R phase transition is only composition driven and thermally insensitive. As a result, a composition axis vertical morphotropic phase boundary (MPB) rather than a tilted polymorphic phase boundary (PPB) was formed. This phenomenon is different from the traditional NKN- and BT-based materials, in which the thermal stability of piezoelectric properties has been seriously challenged because the phase boundary in these two systems is of polymorphism in nature by shifting the PPT temperatures close to room temperature. It is found that the enhanced electrical properties within MPB are attributed to the phase coexistence and the existence of nano-scaled domain morphology, as evidenced by means of synchrotron x-ray diffraction and transmission electron microscopy. In addition, it is also found that the initial R and T phase coexistence of MPB compositions was found to remain up to the proximity of their respective Tc values, resulting in the temperature-insensitive piezoelectric properties. Our study suggests that the current lead-free ceramic would be a very promising piezoelectric material for actuator and sensor applications. N-18 Two Relaxor Transition with Different Local Symmetry in the (K0.5Na0.5)NbO3-BaTiO3 System Yang Yang Xi’an Jiaotong University Piezoelectric ceramic is a kind of functional material which can actualize convert between mechanical stress and electrical voltage. For half a century, the lead zirconate titanate family have been widely used due to their outstanding piezoelectric property. However, owing to the lead toxicity, which harms the environment and human health, the lead-free piezoelectric materials have drawn much attention during the past decades. Among all investigated lead-free systems, the alkali niobate-based ceramic has become one of the most promising candidates due to its large piezoelectric constant and high Curie temperature. The alkali niobate ceramic can easily transform into ferroelectric relaxor by hetero-valent doping, which is in a frozen disordered polarization state with only short-range order. The unique frozen local ferroelectric order makes the relaxor indispensable for some key technological applications from condensers to high-power piezoelectric sensors and actuators. However, the relaxor transition and relaxor structure have rarely been studied. Here we report the complete phase diagram of (1-x)(K0.5Na0.5)NbO3-xBaTiO3 (0≤x≤1) system through X-ray diffractometry and dielectric permittivity measurements over a broad temperature and concentration range. What’s more, we reveal two relaxor transition with different local symmetry and two relaxor structure in one system for the first time, which occur on both sides

of the phase diagram. Our work may light a ray to promote the exploration of the nature of relaxor.

N-19 Preparation of High-Performance (K,Na)NbO3-Based Piezoelectric Ceramics Weizeng Yao, Jialiang Zhang Shandong University School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 Objective: Optimized condition of two-step sintering technique is explored to obtain dense and high-performance (K,Na)NbO3-based piezoelectric ceramics. Methods: Two-step sintering technique is adopted to prepare dense (K0.45Na0.55)0.98Li0.02Nb0.76Ta0.18Sb0.06O3 piezoelectric ceramics. Two-step sintering procedure is set in a way that specimens are first heated to a higher temperature T1 and kept for 1 min to reach an intermediate density, then cooled down and held at a lower temperature T2 for a quite long time t until full densification is completed, which is denoted as T1/(T2,t). Dielectric, piezoelectric and ferroelectric properties, microstructure and domain patterns are systematically studied. Results: The density is found to first increases and then decreases with changing T1 from 1170 oC to 1200 oC, increases gradually with T2 from 1090 oC to 1130 oC, and keeps nearly unchanged with varying t from 4 h to 20 h and then decreases further extending t. All the prepared ceramics show quite similar microstructure of bimodal grain-size distribution with some large grains reaching 15-20 mm and small ones of only about 1 mm. However, distinct differences in domain patterns are observed for these ceramics. The differences are also recognized in the P-E hysteresis loops. The remnant polarization Pr increases firstly and then decreases with the increases of T1, T2 and t. A peak pr value of 24.7 mC/cm2 is reached at 1180 oC /(1120 oC, 20 h). A ceramic sintered at 1180 oC /1120 oC /20h is observed to show some optimum properties, i.e., p ~ 98%, d33 ~ 455 pC/N, kp ~ 0.54, kr ~ 2632, tanδ ~ 0.028, pr ~ 24.7 mC/cm2, and Tc~ 210oC. It has a relative simple domain configuration consisting of a few sets of parallel stripes that correspond to non-180° domains, in contrast to that many watermarks corresponding to 180°-domains are seen in other ceramics prepared under different sintering conditions. In general, d33 is confirmed to show the same variation tendency with kr pr. Conclusion: Sintering conditions of two-step sintering technique can greatly affect the resultant physical properties of a (K,Na)NbO3-based piezoelectric ceramics. A dense (K0.45Na0.55)0.98Li0.02Nb0.76Ta0.18Sb0.06O3 ceramic with excellent piezoelectric properties of d33~ 455 pC/N and kp ~ 0.54 is achieved through the optimization of sintering conditions. The obtained large d33 value is ascribed to simple parallel-stripe domain patterns in the polycrystalline grains and a larger remnant polarization. N-20 Performance Stabilized Lead-Free Piezoelectric Ceramics: (Li, Na, K)(Nb, Ta)O3 Modified by BaZrO3 Fangyuan Zhu1,2, Qing Liu2, Ke Wang2, Jingfeng Li2, Zhi Guo1, Renzhong Tai1 1. Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics,Shanghai Institute of Ceramics, Chinese Academy of Sciences 2. State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University

Legislation arising from health and environmental concerns has intensified research into finding suitable alternatives to lead-based electroceramics. Lead zirconate titanate (PZT) has been dominated commercial manufacturing over several decades to become the market-leading piezoelectric ceramic. Solid solutions based on

sodium potassium niobates (K, Na)NbO3 (shorten as KNN) has become one of the global-desired lead-free piezoelectric ceramics in nowadays due to its superior dielectric and piezoelectric properties. LiTaO3 doped to the perovskite KNN structure (KNNLT) would adjusting Na/K ratio, which enhances the piezoelectric properties and significantly lowers the orthorhombic to tetragonal phase transition (TO-T) to the room temperature. Whereas it introduces the coexistence of O/T phase and promotes the piezoelectric response. Also, KNNLT-BaZrO3 (KNNLT-BZ) solid-solution system has been reported to have the optimal piezoelectric charge coefficient about 340-360 pC/N and high level of unipolar strain up to 0.16% at ambient temperature. Most interesting part for the KNNLT-BZ piezoceramics is the temperature stability of field-induced strain under a wide range of temperatures. The effect of BaZrO3 addition on the piezoelectric response has been researched, which piezoelectric properties suggested it could be one of possible candidates for actuator application design purpose.

N-21 High-Performance Lead-Free Ag(Nb,Ta)O3 Anti-Ferroelectric Energy Storage Ceramics Lei Zhao, Qing Liu, Jing-Feng Li Tsinghua University Recent technology development needs high-performance energy storage materials with a combination of high energy storage density and energy-storage efficiency. Anti-ferroelectric (AFE) ceramics are promising energy storage materials since they have double hysteresis loops with high polarization and small remnant polarization, and so far many studies have been conducted on lead-based ceramics with (Pb,La)(Zr,Sn,Ti)O3 system as a representative. However, due to the growing environmental concerns, lead-free anti-ferroelectric ceramics are highly desired, and AgNbO3 has been focused recently. In this study, Ag(Nb,Ta)O3 ceramics were fabricated by conventional solid-state synthesis in O2 atmosphere. AgNbO3 ceramic shows AFE double hysteresis loop as the applied electric field is above 130 kV/cm and better recoverable energy density (Wrec) of 1.59J/cm3 at 140kV/cm. The addition of Ta can further increase Wrec more than 3.0J/cm3 due to the enhanced anti-ferroelectric property with reduced remnant polarization and enhanced electric field both for AFE to FE phase transition and FE to AFE phase transition. Consequently, Ag(Nb85Ta15)O3 ceramic exhibits excellent energy-storage properties with Wrec=4.2J/cm3 and thermal stability with Wrec=4.0-4.3J/cm3 over 20-120oC. N-22(Invited) Lead-Free Piezoelectric Materials with Prof. Ill-Won Kim for Past 20 Years Jae-Shin Lee, Hyoung-Su Han, Chang-Won Ahn University of Ulsan This special talk has been prepared for commemorating the contribution to our piezoelectric community by Prof. Ill-Won Kim, who will retire on Feb of 2017 at University of Ulsan (UOU). Since moving to UOU in 1993, I have co-worked with Prof. Ill-Won Kim in the field of lead-free piezoelectric materials and their application to ultrasonic sensors and multilayer actuators. More than 100 undergraduate and graduate students have attended the long time collaboration between MSE (School of Materials Science and Engineering) and DOP (Department of Physics). Consequently, UOU has greatly contributed to the development of new lead-free materials and their applications as well as education of human resources. At the same time, Prof. Kim has actively participated in a wide range of international conferences on ferroelectrics and piezoelectrics. In addition, he has contributed a lot to many successful conferences as a member of organizing committee and as a big attending group. This talk looks back on the past 20 years on the basis of my memory with Prof. Kim.

N-23(Invited) Polarization Twist in Perovskite Ferrielectrics: A New Mechanism of Piezoresponse in Polar Perovskite Oxides Yuji Noguchi Yuuki Kitanaka, Masaru Miyayama The University of Tokyo Objective: The electro-mechano property of ferroelectrics governs the performance of the piezoelectric devices such as sensors, actuators and ultrasonic imagings. It has recently been understood that a phase transition (including polarization rotaion) by applying an electric field (E) is the origin of the superior electro-mechano property. Here, we report a piezoresponse up to 1000 pm/V originating from a new mechanism in ferrielectric single crystals, termed ‘polarization twist’. Methods: Single BNT–7% BT crystals were grown by a top-seeded solution growth method at a high oxygen pressure (Po2 = 0.9 MPa). First, BNT–BT powders prepared via a solid-state reaction were mixed with a flux composed of Bi2O3, NaF and BaCO3 and placed in a platinum crucible. The mixture was soaked at 1,100 °C for 4 h, slowly cooled to 1,070 °C at a rate of −2 °C/h, and then cooled to room temperature. Results: Single-crystal structural analysis under electric fields demonstrate that BNT–7% BT crystals exhibited an extremely high piezoelectric strain constant d33 up to 1000 pm/V. The structural analyses based on neutron powder diffraction and single-crystal XRD reveale that the high d33 originates from a polarizaiton enhancement accompanied by octahedral rotation in the P4bm ferrielectric phase. In situ X-ray diffraction (XRD) analysis using high-energy synchrotron radiation demonstrates that electric fields induce an extended polar displacement accompanied by nonpolar octahedral rotations in ferrielectric crystals, as if twisted polarization relaxes and stretches. Conclusions: The twisted polarization creates a large piezoresponse and finally changes to a ferroelectric polarization. Our simulations based on density functional theory and phenomenological theory show that this concept stems from a structural coupling between nonpolar octahedral rotation and polar distortion. N-24(Invited) Dielectric and Piezoelectric Properties of “Lead-Free” Piezoelectric Rhombohedral BTZ-BCT Single Crystals Ho-Yong Lee1, Dong-Ho Kim2, Jong-Yeb Lee2 1. Sunmoon University 2. Ceracomp Co., Ltd.

Rhombohedral BTZ-BCT single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method and their dielectric and piezoelectric properties are also characterized. Measurements show that (001) BTZ-BCT single crystals have an electromechanical coupling factor (k33) higher than 0.9, piezoelectric charge constant (d33) of about 1,000 [pC/N], and piezoelectric voltage constant (g33) higher than 40 [x10-3 Vm/N]. Especially the d33 of (001) BTZ-BCT single crystals was by about five times higher than that of their ceramics. Because their electromechanical coupling factor (k33) and piezoelectric voltage constant (d33, g33) are higher than those of soft PZT ceramics, it is expected that rhombohedral (001) BTZ-BCT single crystals can be used as “lead-free” piezoelectric materials in many piezoelectric applications such as actuator, sensor, and transducer. N-25(Invited) High Performance Hybridized Nanogenerators for Scavenge Mechanical and Thermal Energies

Ya Yang Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences Converting mechanical and thermal energies from the environment into electric energy has attracted increasing attentions in past decade not only for dealing with the global energy crises, but also achieving the self-powered electronics. However since the mechanical and thermal energies are not always available at the same time, it is expected to develop a hybridized nanogenerator to simultaneously/ individually scavenge the two kinds of energies. Previous investigations are mainly focused on how to integrate the different naongenerators in series or in parallel. In fact, some nanomaterials have the multi-physical properties such as PVDF with piezoelectric, pyroelectric, and triboelectric properties, which may be utilized to fabricate a hybridized nanogenerator with one material structure but exhibiting different functions for simultaneously scavenging different kinds of energies. Due to that the different nanogenerators have the same materials and current/voltage circuits, the coupling effect may appear in the hybridized device. Here we fabricate a highly transparent, flexible, and hybridized nanogenerator based on a PVDF nanowires-PDMS composite film as the triboelectric layer, a polarized PVDF film as both the piezoelectric and pyroelectric layers, and ITO electrodes. The hybridized nanogenerator with one device structure and same electrodes can simultaneously deliver output current/voltage signals of the triboelectric nanogenerator, piezoelectric nanogenerator, and pyroelectric nanogenerator. As compared with the individual energy harvesting units, the hybridized nanogenerator has a much better charging performance for a 10 uF capacitor. Refs: (1) Shuhua Wang, Zhong Lin Wang*, and Ya Yang*. "A one-structure-based hybridized nanogenerator for scavenging mechanical and thermal Energies by triboelectric-piezoelectric-pyroelectric effects", Advanced Materials, 2016, 28, 2881-2887. (2) Shuhua Wang, Xiaojing Mu, Ya Yang*, Chengliang Sun, Alex Yuandong Gu, and Zhong Lin Wang*."Flow-driven triboelectric generator for directly powering a wireless sensor node", Advanced Materials, 2015, 27, 240-248. (3) Kewei Zhang, Zhong Lin Wang*, and Ya Yang*. "Conductive fabric based stretchable hybridized nanogenerator for scavenging biomechanical energy", ACS Nano,2016, inpress. (4) Shuhua Wang, Xue Wang, Zhong Lin Wang*, and Ya Yang*."Efficient scavenging of solar and wind energies in smart city", ACS Nano, 2016, in press. (5) Xue Wang, Shuhua Wang, Ya Yang*, and Zhong Lin Wang*. "Hybridized electromagnetic-triboelectric nanogenerator for scavenging air-flow energy to sustainably power temperature sensors", ACS Nano, 2015, 9, 4553-4562. N-26(Invited) Large Transverse Piezoelectric Properties of Lead-Free Bi0.5(Na0.82K0.18)0.5TiO3 Films Ill Won Kim, Song A Chae, Sung Sik Won, Won Seok Woo, Hae Jin Seog, Chang Won Ahn University of Ulsan The ferroelectric and piezoelectric properties of Bi0.5(Na1-xKx)0.5TiO3 (x=0, 0.18 and 0.25) films deposited on Pt(111)/TiO2/SiO2/Si(100) substrates using a chemical solution deposition technique were examined as part of an ongoing study into the development of lead-free piezoelectric films. The effective transverse piezoelectric coefficient (e*31,f) was examined to assess the potential applications of these piezoelectric films for device applications using the Bi0.5(Na0.82K0.18)0.5TiO3 (BNKT18) cantilever, which is the morphotropic phase boundary composition in the Bi0.5(Na1-xKx)0.5TiO3 system. The BNKT18 cantilever showed good linearity of piezoelectric

displacement with low hysteresis under an applied field, and exhibited a high effective transverse piezoelectric coefficient (e*31,f) of ~5.15 C/m2 and a figure of merit ((e*31,f)2/ε0εr) of 3.8 GPa, which are comparable to the preferred oriented lead-free piezoelectric and lead zirconate titanate thin films. This suggests that the BNKT18 film is a potential candidate for lead-free piezoelectric film devices. N-27(Invited) Recent Developments on Lead Free Ferroelectric/ Piezoelectric Materials Shujun Zhang1,2, Yalin Qin3,4, Jialiang Zhang3 1. Wuhan University of Technology 2. University of Wollongong 3. Shandong University 4. Qingdao University Objective: Lead free ferroelectrics have been hot topic for last ten years. Recent reports on lead free can be categorized into three main families: 1. BaTiO3 (BT), 2. K0.5Na0.5NbO3 (KNN) and 3. Na0.5Bi0.5TiO3 (NBT) based materials. We will survey the developments of these lead free systems in this presentation. Method: In this work, the scientific and technical impacts of these materials are contrasted with the “soft” and “hard” PZTs. On the scientific front, the intrinsic nature of the dielectric and piezoelectric properties are presented in relation to the existence of an MPB. Analogous to PZT, enhanced properties are noted for MPB compositions in the NBT-BT, but offer properties significantly lower. The consequences of a ferroelectric to antiferroelectric transition well below TC further limits their usefulness. Though comparable with respect to TC, the high levels of piezoelectricity reported in KNN based materials are result of enhanced polarizability, associated with the O-T polymorphic phase transition (PPT) being compositionally shifted downward. As expected, the properties are strongly temperature dependent, while degradation occurs through the thermal cycling between the two distinct ferroelectric domain states. Technologically, the lead free materials are discussed in relation to general applications, including actuators and transducers. Finally, manufacturability plays a very important role in the implementation of materials into actual devices. Results and Conclusions: For fully understanding and successful implementation of the lead free materials, the following progresses have been achieved: For KNN family, the PPT was further shift downward to below room temperature, to improve the temperature stability while maintaining high piezoelectric properties. For the lead free ceramics, acceptor dopant strategy has been adopted to reduce the power dissipation, for the potential high power application. The material properties were evaluated at hard drive condition and compared to that measured at small signal condition, revealing modified NBT-based lead free possessing very stable mechanical Q as function of drive field, superior to “hard” PZTs, closely associated with their high coercive field, ~ 35kV/cm. Fundamentally, in-situ TEM was employed to study the domain structure as a function of applied electric field, and the relationship between the microstructure and macroscopic properties has been established. N-28(Invited) Growth, Electrical and Mechanical Characterization of Modified Calcium Aluminate Silicate Piezoelectric Single Crystals Hiroaki Takeda1, Kyohei Yoshida1, Hiroki Okudera2, Lebbou Kheirreddine3, Takuya Hoshina1, Takaaki Tsurumi1 1. Tokyo Institute of Technology

2. Kanazawa University 3. University of Lyon

Objective: The aim of this study is to find the most appropriate single crystal for high-temperature piezoelectric sensor devices. We have focused on calcium aluminate silicate Ca2Al2SiO7 (CAS) crystals with melilite-type structure. From our previous reports, the melilite crystals should be promising candidates for piezoelectric materials. However, they are characterized by a distinct cleavage plane, which is normal to the crystallographic c-axis. This cleavage plane may cause low mechanical strength and thus narrow the range of their potential target applications. Therefore, we attempted to synthesize modified CAS single crystals with higher mechanical strength. Methods: Modified CAS single crystals were grown by a laser-heated pedestal growth method and a Czochralski (Cz) technique. The dielectric, piezoelectric, and elastic compliance constants of CAS single crystals were determined with Agilent 4294A Impedance/Gain Phase Analyzer. Compression tests were performed to determine the rupture strength of crystal substrates by using a texture analyzer (TA.XT.PLUS). Results: Two kinds of CAS based solid solution single crystals were successfully grown by the Cz method. One of them is the La-doped CAS (La-CAS) and another is Sr-substituted CAS (Sr-CAS). By the resonance method, a apparent length-extensional piezoelectric modulus d’31 was determined using (XYt)45o-cut plate samples. The d’31 values (3 pC/N) of both the La- and Sr-CAS crystals were almost the same as that of CAS. The electrical resistivity at room temperature of the La-CAS crystal was 1011 Wcm order and that of Sr-CAS crystal was 1012 Wcm order. Then, the mechanical strength of Sr-CAS was measured and compared to that of CAS. The rapture strength of Sr-CAS crystal was 230 MPa, which was 1.2 times higher than that of CAS crystal. Conclusion: Since Sr substitution succeeded in improving the shortages of the CAS crystals for pressure sensor applications, we believe that Sr-CAS can be applicable for manufacturing high-temperature piezoelectric sensors. N-29(Invited) A Brief Review on the Relaxor Ferroelectrics for Better Understanding Incipient Piezoelectricity Chang Won Ahn1, Gwangho Choi1, Jae-Shin Lee2, Ill Won Kim1, Younghun Hwang3, Ke Wang4, Wook Jo3 1. Department of Physics and EHSRC, University of Ulsan, Ulsan 44610, South Korea 2. School of Materials Science and Engineering2, University of Ulsan, Ulsan 44610, South Korea 3. Ulsan National Institute of Science and Technology, UNIST-gil 50, Ulsan, 44919, Republic of Korea 4. School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China Recently developed lead-free incipient piezoceramics are promising candidates for off-resonance actuator applications with their exceptionally large electromechanical strains. Their commercialization currently faces three critical challenges: high driving electric field required for delivering the large strains, large strain hysteresis inappropriate for precision devices, and relatively large temperature dependence. We demonstrate that instead of utilizing the incipient piezoelectric strains, harnessing the maximum possible electrostriction provides a highly effective way to resolve all the challenges. Ceramics are texturized by a reactive template grain growth technique for the concept to be realized experimentally. The manufactured textured ceramic is featured by Smax/Emax of 995 pm/V and the electrostrictive coefficient Q33 of 0.049 m4/C2, which are as large as those of single crystals. We believe that the current work is sure to draw a significant attention from the community members as a step-forward towards the way the lead-free ceramic community should proceed. As well, we are sure that the concept we present here can be easily transferred to other disciplines in designing functional properties of various materials.

N-30 Low-Temperature Sintering and Microstructure Development in CuO-Doped (K,Na)NbO3 Ceramics for Multilayered Piezoelectric Devices Jung Hwan Kim1, Dae Su Kim1,2, Seung Ho Han2, Hyung-Won Kang2, Hyeung-Gyu Lee2, Jeong Seog Kim1, Chae Il Cheon1 1. Hoseo University 2. Korea Electronics Technology Institute

There have been considerable efforts to develop lead-free piezoelectric ceramics for replacing Pb-based piezoelectric ceramics due to a global environment issue. (K,Na)NbO3 (KNN) is one of the highest potential candidates for a lead-free piezoelectric ceramic. A demand for multilayered piezoelectric ceramics is increasing due to their advantages such as a low operating voltage and high piezo-response. In this work, KNN ceramics with grains of a few micrometers or less were prepared at sintering temperature around 900oC for multilayered piezoelectric devices. CuO-doped KNN-based ceramics showed dense microstructures with abnormal grains and good piezoelectric properties at the sintering temperature in air. A two-step sintering and a sintering in nitrogen atmosphere were tried in this work to inhibit the abnormal grain growth and to enhance piezoelectric properties. Densification, microstructure development, and piezoelectric properties in samples sintered at various conditions were investigated. N-31 Domain Evolution Related with Phase Transition in Lead-Free Piezoelectric Li-Doped KNN/SrTiO3(100) Epitaxial Thin Films Jin Luo, Wei Sun, Zhen Zhou, Jing-Feng Li Tsinghua University KNN-based ceramics, as competitive lead-free counterparts, have attracted substantial attentions because of the high piezoelectric response induced by the orthorhombic-tetragonal phase transition. The evolution of domain structure is of great importance for understanding fundamental physics of piezoelectric materials. In this work, 6% Li doped KNN epitaxial thin films were prepared using a sol-gel method and in-situ domain structure has been studied during heating and cooling cycles from room temperature to 190oC by means of piezoresponse force microscopy. A change in domain morphology occurred upon heating to 110oC, and significant changes were observed from temperature 130oC to 150oC. The domain morphology transformation was attributed to the orthorhombic-tetragonal phase transition. No obvious changes in domain structure occurred when temperature cooled from 190oC back to 150oC, but a gradual change was observed from 130oC to room temperature. After one heating and cooling cycle, the domains at room temperature became different from original ones. The results demonstrate that some domains in an orthorhombic phase of KNN are highly active and irreversible when temperature changed. It was also revealed that the orthorhombic-tetragonal phase transition occurred in a wide temperature range from 90oC to 190oC. N-32(Invited) Structural Characteristics of Perovskites Containing Lone-Pair Cations Yoshihiro Kuroiwa Hiroshima University

Lead containing ceramics such as ferroelectric lead zirconate titanate (PZT) are the world's most widely studied and used piezoelectric oxide materials. Lead and its compounds are generally toxic, and have been considered as environmental health hazardous materials. However, because of no suitable substitute for the lead containing ceramics in the total performance, the use of PZT ceramics and the related materials is still continued. The significant enhancement of the piezoelectric response in the PZT ceramics originates primarily from the large polar lattice distortion caused by the lone-pair cation Pb2+ and the morphotropic phase boundary (MPB) which divides the regions of ferroelectric phase into two parts in the phase diagram. By considering the Bi3+ ion having the electron configuration of being analogous to the Pb2+ ion, the lone-pair cation Bi3+ can be a candidate for the substitution of the Pb2+ ion in the lead containing ceramic systems. Nowadays, numerous bismuth containing ceramics are suggested for the candidates of lead-free piezoelectric ceramics. In this symposium, the structural characteristics found in the electron density maps in perovskite-type ceramics containing lone-pair cations such as Pb2+ and Bi3+ are reviewed to discuss the vital role of the lone -pair cation on the emergence of the polar lattice distortion. Our group has been devoted to visualizing the electron density distribution of perovskite-type ferroelectrics by analyzing the synchrotron-radiation X-ray powder diffraction (SXRD) data measured at SPring-8 using the maximum entropy method (MEM)/Rietveld method. We have applied the method to PbTiO3, and showed the first experimental evidence for covalency between the Pb and O ions in the whole electron density distribution [Y. Kuroiwa et al.: PRL 87, 217601 (2001)]. The valence electron density distribution is, however, more informative in many cases from the viewpoint of chemistry of chemical bonding. In our recent study, we have succeeded in evaluating the valence electron density distributions in the outer shells of atoms accurately from the SXRD data for various perovskites containing lone-pair cations. The obtained results provide direct experimental evidence that the electronic polarization caused by the Pb2+ or Bi3+ ion is clearly visualized in the valence electron density distribution. N-33(Invited) Unique Piezoelectric Properties of the Monoclinic Phase in Pb(Zr,Ti)O3 Ceramics Revealed by In-Situ High-Energy Synchrotron Diffraction Jun Chen1, Longlong Fan1, Yang Ren2, Xianran Xing1 1. Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China 2. X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA Revealing the piezoelectric mechanism near morphotropic phase boundary (MPB) is a key point for the development of piezoelectric materials. Recently, the observation of the monoclinic phase at the MPB provided a crystallographic insight to comprehend the mechanism of excellent piezoelectric properties. First-principle calculations have predicted that the monoclinic phase possesses a gigantic intrinsic piezoelectric property. Unfortunately, there exist no experimental investigations to reveal the role of the monoclinic phase in the piezoelectric behavior. In this work, a single monoclinic phase has been identified in the Pb(Zr0.535Ti0.465)O3 (PZT) ceramics at room temperature by in-situ high-energy synchrotron diffraction, and its response to electric field has been characterized for the first time. Unique piezoelectric properties of the monoclinic phase of PZT in terms of large intrinsic lattice strain and negligible extrinsic domain switching have been observed. The extensional strain constant d33 and the transverse strain constant d31 are calculated to be 520 and -200 pm/V, respectively. These large piezoelectric coefficients are mainly due to the large lattice strain, with very little extrinsic contribution from domain switching.

The unique properties of the monoclinic phase provide new insights into the mechanisms responsible for the piezoelectric properties at the MPB. The present results can play as a reference for theoretical calculation and also be helpful for the understanding of the origin of excellent piezoelectric properties in other Pb or Pb-free MPB systems in the future. Reference [1] L. L. Fan, J. Chen, Y. Ren, Z. Pan, L. X. Zhang, X. R. Xing, Phys. Rev. Lett. 2016, 116, 027601. N-34(Invited) Strong Electromechanical Coupling in Paraelectric Phase Hao Tian, Bo Yao, Chengpeng Hu Department of Physics, Harbin Institute of Technology The electro-mechanical coupling is normally not expected in the paraelectric phase of ferroelectrics because of the absence of piezoelectric effect. While an electro-mechanical resonance only excited by a weak (less than 10 V/mm) AC electric field is observed in the paraelectric KTa1-xNbxO3 crystals near the phase boundary. We show that the transformation from disordered to ordered arrangement of polar nanoregions under the electric field enhances the electrostrictive effect near phase boundary, which is responsible for the intensive electro-mechanical coupling. This result establishes the essential correlations between the polar nanoregions and macroscopic physical properties for relaxor ferroelectrics near the para-ferroelectric phase boundary. N-35(Invited) Relationship among Phase Transition, Phonon Mode, and Electronic Structure of Ferroelectric Oxides Zhigao Hu, Jinzhong Zhang, Kai Jiang, Junhao Chu East China Normal University Ferroelectric oxides are extraordinarily attractive from fundamental and technological point of views due to excellent electrical, magnetic, structural, and optical properties [1]. It should be emphasized that optical properties, especially for electronic transitions, have been scarcely investigated. Moreover, one can derive the phase transformation by checking the variation on electronic transition and lattice vibrations with the temperature and doping composition. Keep this in mind, we carried out lots of solid state spectroscopic measurements for ferroelectric crystals, ceramics, and films to discover critical information on optical response and phase transformation, etc. In the Talk, we will present some interesting results on optical properties from ferroelectric single crystals and films (PZNT, NBBT, KNN) using variable-temperature Raman scattering and spectroscopic ellipsometry [2-6]. For example, the spectra from MnO2-doped KNN exhibit a competition between a soft mode and a relaxation mode upon heating across the diverse transitions. The progressive change in the conflicting displacive mechanism (soft mode) and order-disorder (relaxation mode) can explain the origin of the successive orthorhombic-tetragonal-cubic phase transitions. Moreover, the polymorphic phase transition between orthorhombic and tetragonal structures can be confirmed through the observation of thermotropic phase boundaries for MnO2-doped KNN. On the other hand, the second derivative of the complex dielectric functions from PZNT and NBBT crystals reveals a series of interband electronic transitions. Depending on the temperature evolution of electronic transitions, the structural variations can be observed. Furthermore, Ab initio density functional theory calculations have been carried out to explain the above phenomena. The present results can establish a quantitative relationship between the electronic transition and phase transformation for ferroelectric

oxides. References: 1. Z. G. Ye, MRS Bullentin 34: 277 (2009). 2. J. Z. Zhang, W.-Y. Tong, J. J. Zhu, J. Y. Xu, Z. H. Duan, L. P. Xu, Z. G. Hu, C.-G. Duan, X. J. Meng, Z. Q. Zhu, and J. H. Chu, Phys. Rev. B 91: 085201 (2015). 3. L. P. Xu, K. Jiang, J. Z. Zhang, G. S. Xu, Z. G. Hu, and J. H. Chu, Appl. Phys. Lett. 106: 122901 (2015). 4. Q. L. Deng, J. Z. Zhang, T. Huang, L. P. Xu, K. Jiang, Y. W. Li, Z. G. Hu, and J. H. Chu, J. Mater. Chem. C 03: 8225-8234 (2015). 5. T. Huang, S. Guo, L. P. Xu, C. Chen, Z. G. Hu, H. S. Luo, and J. H. Chu, J. Appl. Phys. 117: 224103 (2015). 6. T. Huang, Z. G. Hu, G. S. Xu, X. L. Zhang, J. Z. Zhang, and J. H. Chu, Appl. Phys. Lett. 104: 111908 (2014). N-36 Observation of Dual Relaxation Processes in Barium Titanate during Paraelectric-Ferroelectric Phase Transition Zhi Guo1, Mingjun Zhang1, Renzhong Tai1, Haisu Luo2 1. Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics,Shanghai Institute of Ceramics, Chinese Academy of Sciences 2. Shanghai Institute of Ceramics, Chinese Academy of Sciences

Measurement of polarization correlation for polarization clusters during paraelectric-ferroelectric phase transition in barium titanate. Recently, polarization clusters were investigated as a new approach to research the mechanism of this phase transition. The coexistence of displacive and order-disorder processes was considered closely related to the formation of polarization clusters. However, the roles played by these two mechanisms during this phase transition is still unclear and dual relaxation processes for polarization clusters have never been directly observed. Base on the improved He-Ne laser photon correlation spectroscopy (PCS) technique, we actually observe this dual relaxation processes, clarifying the role of the dynamics process of polarization clusters during this phase transition and revealing the origin of the large dielectric response of this prototype ferroelectric. N-37 A Strain Driven Phase Transition in La-Doped BiFeO3 on Si Deyang Chen1,2,3, Chris Nelson2, Xiaohong Zhu2, Jian Liu2, Ya Gao2, Dechang Zeng3, Xingsen Gao1, Darrel Schlom4, Liu Junming1, Ramamoorthy Ramesh2 1. South China Normal University 2. University of California, Berkeley 3. South China University of Technology 4. Cornell University

Objectives: Strain induced ferroelectric to ferroelectric (FE-FE) phase transition from rhombohedral-like (R) phase to tetragonal-like (T) phase in BiFeO3 films, with enhanced piezoelectricity near the R/T morphotropic phase boundary (MPB), has been widely studied. Few reports, however, have focused on a strain driven orthorhombic (O) to rhombohedral-like (R) phase transition and the possible formation of an O/R MPB. We are prompted to explore three questions: (i) is it possible to achieve a strain driven O to R phase transition in this system, (ii) does the O/R MPB exist, and (iii) are the O to R phase transitions also FE-FE phase transitions? Methods: We grew a series of epitaxial La doped BiFeO3 (LBFO) films with thickness of 20~125 nm on SrTiO3

buffered (001) Si substrates with SrRuO3 as bottom electrode by pulsed laser deposition (PLD). A combination of x-ray diffraction (XRD), reciprocal space mapping (RSM) and transmission electron microscopy (TEM) was used for the structural characterization. Ferroelectric properties were measured using piezoresponse force microscopy (PFM). Results: We find that epitaxial strain from Si substrate can stabilize a rhombohedral structure of LBFO in 20 nm films and intermediate strains position LBFO into a nanoscale mixture of rhombohedral and orthorhombic phases in 30-100 nm films and finally full strain relaxation in films thicker than ~125nm leads to the orthorhombic phase. In the O/R mixtures, we show that O and R phases can coexist with O phase domains larger than 10 nm in width. Also, atomically sharp O/R morphotropic phase boundary (MPB) is observed. Conclusions: Our studies have revealed the ability of the epitaxial strain induced orthorhombic to rhombohedral phase transitions in LBFO thin films on Si. Furthermore, we demonstrate that the orthorhombic to rhombohedral phase transitions are antiferroelectric to ferroelectric phase transitions. Our findings open a new pathway to drive AFE-FE O-R phase transitions in LBFO and provide a route to study O/R MPB. N-38 Giant Electrostrictive Strain and Its Origin in NaNbO3-BaTiO3 Lead-Free Relaxor Ferroelectric Ceramics He Qi, Jian Fu, Ruzhong Zuo Institute of Electro Ceramics & Devices, School of Materials Science and Engineering, Hefei University of Technology, Hefei, 230009, P.R. China The electrostrictive effect is a fundamental property for a dielectric which changes its dimensions under an applied bias electric field. The electric field induced longitudinal strain (S33) can be expressed by a quadratic function of the polarization (P3), S33=Q33P3

2, where Q33 is the electrostrictive coefficient. Generally, the electrostrictive effect is very weak in most perovskites, and the electrostrictive strain is usually small compared with that from the converse piezoelectric effect. However, the electrostrictive effect offers several unique advantages such as little or no strain hysteresis up to high frequencies, a fast response speed, reduced aging effects, and no poling requirement. Thus, comparing with classical ferroelectrics, these materials with large electrostrictive strain have potentials in actuator applications owing to the good reproducible and non-hysteretic deformation responses. In this work, a highly pure hysteresis-free electrostrictive strain was reported in (1-x)NN-xBT lead-free solid-solution ceramics, which exhibit a high electrostrictive coefficient Q33 of ~0.046 m4/C2 twice as large as those of Pb- and Bi-based perovskite relaxor ferroelectric ceramics. A hysteresis-free large electrostrictive strain of ~0.148% up to at least 70 Hz was obtained in the x=0.25 sample. The analysis indicates that the cations exhibiting strong ionic interaction with O are favor to the high electrostrictive coefficient Q33 but adverse to the polarization P3. Therefore, for NN-based relaxor ferroelectrics, a large electrostrictive strain would be generated owing to high Q33 from a strong A-O ionic bond and simultaneously high polarization response (P3) from B-site ionic ferroelectric displacement. These results indicate that the NN-xBT ceramics would have excellent potential for applications of lead-free actuator ceramics and this work also provides a universal method for designing high performance electrostrictive materials. N-39 Effects of La Doping on Microstructure and Ferroelectric Properties of BLTN Lead-Free Ceramics Nana Shao Shanghai Institute of Ceramics, Chinese Academy of Sciences

Lead-based EO ceramics such as PLZT have been widely used for decades. Because of the toxicity of lead, lead-free EO ceramics have received increasing attention from the view point of environment in recent years. Lead-free Ba6-1.5xLaxTi2Nb8O30 (0≤x≤7%) ceramics were synthesized by conventional solid state reaction sintering. Effects of lanthanum oxide (La2O3)-doping on the microstructure and electrical properties of Ba6Ti2Nb8O30 (BTN) were investigated. The results reveal that the sintering temperature enhance with the increase of La2O3 content, and the densities of all samples with La doping are bigger than that of pure BTN ceramics. The SEM results show that the grain sizes decrease with increasing La doping. The electrical properties reveal that the dielectric constants increase first, and then decrease with increasing La doping. The Tm shifted to lower temperature decreased while the arnount of La were inereased. The ceramic with 4% La has the optimized electrical properties, the saturated polarization Ps is 4.48μC/cm2 and the remanent polarization is 1.09 μC/cm2, the coercive electric field is 4.14kV/cm. Samples of transmittance are testing. N-40 Domain Configuration and Thermal Stability of (K0.48Na0.52)(Nb0.96Sb0.04)O3-Bi0.50(Na0.82K0.18)0.50ZrO3 Piezoceramics with High d33 Coefficient Yalin Qin1,2,3, Jialiang Zhang2, Weizeng Yao2, Chaojing Lu1, Shujun Zhang3,4 1. College of Physics; Key Laboratory of Photonics Materials and Technology in Universities of Shandong, Qingdao University, Qingdao 266071, Shandong, P. R. China 2. School of Physics; State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, P. R. China 3. Materials Research Institute, Pennsylvania State University, Pennsylvania 16801, USA 4. Institute for Superconductor and Electronic Materials; Australia Institute of Innovative Materials, University of Wollongong, Wollongong, NSW 2500, Australia

Domain is the key point to clarify the mechanism of property engineering in ferroelectric materials. In viewpoint of high-temperature application, it is desirable to develop a KNN-based ceramic with high d33 and TC, while maintaining high temperature stability. Recently, a high d33 of 490 pC/N (TC~220oC) in KNN-based ceramics with R-T MPB was reported, comparable to PZT 5H (d33~590 pC/N and TC~200oC), but the thermal-stability characteristics and the origin mechanism of the high piezoelectric properties associated with the R-T MPB are yet unclarified. In this work, we prepared 0.9625(K0.48Na0.52)(Nb0.96Sb0.04)O3-0.0375Bi0.50(Na0.82K0.18)0.50ZrO3 (KNNS0.04-0.0375BNKZ) ceramics. Sb5+ and Bi(K, Na)ZrO3 were chosen to combinatorially enhance TR-O and decrease TO-T, in order to form a R-T phase boundary at room temperature. The thermal stability was studied over a broad temperature range, involving the R-T phase transition region. Domain configurations before and after poling were studied by SEM on acid etched ceramic surfaces. The underlying mechanism of the excellent piezoelectric properties and good thermal stability were discussed from a microstructure perspective. Properties with both high d33 and medium TC (d33~460pC/N, TC~267oC) have been achieved in KNNS0.04-0.0375BNKZ ceramics. Short domain segments (before poling), long domain stripes with wedge-shaped or furcated ends (after poling), were found to be typical domain configurations. Minor piezoelectric property variations (<6% over temperature range of -50~100oC) were observed as a function of temperature, showing a good thermal stability. The reduced elastic energy, lattice distortion and internal stress due to the coexistence of rhombohedral and tetragonal phases, result in much easier domain reorientation and domain wall motion, which are responsible for the high piezoelectric properties. The extrinsic contribution to the total piezoelectricity from irreversible domain switching was estimated to be around 50%. In addition, nano-domains (50 ±2 nm) were found to be assembled

into domain stripes after poling, believed to benefit the high piezoelectric properties, meanwhile not causing much thermal instability due to the small quantity.

Poster N-P01 The Preparation of (K,Na)NbO3 Powders with Wide Grain Size Distribution Lin-ling Li, Kai-li Jia, Yuhua Zhen College of Science, China University of Petroleum In this study, we aimed to obtain (K, Na)NbO3 powders with wide grain size distribution. (K,Na)NbO3 powders have been successfully synthesized by different methods (hydrothermal method, sol-gel method, molten-salt method). The experiment results showed that the methods of hydrothermal and sol-gel can’t control grain size of the (K,Na)NbO3 powders effectively . The grain size of (K,Na)NbO3 powders which can be only tailored by the molten-salt method through controlling the starting oxide powder morphology, as well as crystallization temperature. In addition, the experimental parameters would not influence the final (K, Na)NbO3 powder grain size if the initial powders are not ball milled. Furthermore, we have found that the crystallization temperature could change the powders grain size monotonously. The (K,Na)NbO3 powders synthesized by molten salt method were distributed from nanoscale to micron level, which can lay the foundation for further research on the grain size effect of (K,Na)NbO3 lead free piezoelectric ceramics. N-P02 Synthesis and Sintering Performances of Nanometer Silicon Nitride Powder Xuan Zhao, Haiyan Chen, Chenyang Shu, Lihua Dong, Yansheng Yin Shanghai Maritime University Purpose：Silicon nitride (Si3N4) is an important structural ceramic material. As a super hard material, it is characterized by excellent wear resistance, corrosion resistance, high temperature resistance and fatigue toughness, bending strength and thermal shock resistance as well as lubricity. It is an atomic crystal, and resists oxidation at high temperature. Furthermore, it can resist cold and heat shocks. Therefore, silicon nitride is widely utilized in various fields of aerospace, machinery, electronic and electric power, and chemical engineering, etc. The proper utilization of sintering aids can effectively improve the hardness and thermal conductivity of silicon nitride ceramic materials, increase the fracture toughness of materials, and enhance the perfection of material performance. Methods: Takes secondary products of polycrystalline silicon, silicon tetrachloride (SiCl4) and liquid ammonia (NH3), as the main raw materials, and silane as catalyst, this paper adopts synthesis technology of induction plasma heating and proceeds catalysis through silane. Finally, two-step microwave heat treatment is adopted to control the size, particle shape and crystal of powder particles, and the obtained powders are further characterized. Microwave is a kind of ultrahigh frequency electromagnetic wave, and its frequency ranges from 300 MHz to 300 thousand GHz. The principle of microwave heating is to utilize the vibrations and frictions of polar molecules within the material in the electromagnetic field transformed in high speed and generate a mass of heat so as to heat the material. Compared with the traditional electric heating methods, microwave heating possesses a strong penetration ability, which can directly affect the heated material. The inside and outside of the materials could be heated concurrently in a short period of time. The heating is more thoroughly with high efficiency. Furthermore, there is no temperature gradient of the heated material. Materials with different dielectric constants are different in

the absorption loss of microwave. As for the materials with lower dielectric constants, the auxiliary material could be evenly added for rapid heating. There is no thermal inertia in microwave heating. The heating of material could be immediately stopped or slowed down by turning off the microwave source or reducing the power, which is of great significance for the control of the reaction which is sensitive to temperature. In addition, microwave can generate catalytic effects on some reactions. In other words, the reaction system can react at a lower temperature, or possesses a faster reaction rate at the same temperature. This paper takes the synthetic nanometer silicon nitride powder and imported α-Si3N4 powder as sintering raw materials, Y2O3 and Al2O3 as sintering aids. The sintering temperature is 1450-1550℃, and the sintering time is 1 hour. The high density silicon nitride ceramic materials with different contents of sintering aids are prepared by spark plasma sintering (SPS) under the condition of uniaxial pressure of 45MPa. Spark plasma sintering is a phenomenon that generates spark discharge between the powder particles by pulse direct current. The effects of high temperature field, discharge impact pressure, surface cleaning effect, and power plant diffusion are generated to achieve rapid sintering. It is characterized by rapid sintering process, high rate of temperature fall, short soaking time, and low sintering temperature. Therefore, it could effectively inhibit the grain growth. Pressurization during the sintering process could realize the rapid preparation of high density and ultrafine structural materials. Spark plasma sintering could utilize pulse energy, discharge impulse pressure and Joule heat to generate local high temperature up to thousands or even ten thousands Celsius degree instantaneously. The crystal surfaces are evaporated and melted under high temperature, which leads to the excitation of the particle surfaces and intensifies the volume diffusion and grain boundary diffusion. Rapid heating and cooling rates and short sintering time effectively prevent from grain growth and shorten the production cycle so as to save energy. Results: Based on the analysis of microstructure of the prepared silicon nitride materials and the characterization of phase analysis, this paper studies the mechanism of action of the change of sintering aids on phase transformation rate, grain boundary phase composition and grain size of silicon nitride ceramics materials. The influence rule of the contents of sintering aids on mechanical property and thermal conductivity of materials is investigated through the system testing of mechanical properties of materials. Conclusions: The main research contents and conclusions of this paper can be summarized as follows: （1）The particle size of the silicon nitride powder synthesized through the induction plasma heating is smaller than 50nm. The content of α-Si3N4 is greater than 94.5%. The content of Fe is smaller than 0.001%. The content of O is smaller than 0.03%. The content of Cl is smaller than 1.0%. （2）Synthesis of silicon nitride utilizes silane as the catalyst, which promotes the reaction of silicon tetrachloride and ammonia gas, reduces the addition of ammonia, and improve the efficiency of raw material synthesis. Induction plasma heating synthesis of silicon nitride can realize continuous production. The two-step microwave heat treatment process effectively controls the particle size, particle shape and crystal shape of powders. （3）Silicon nitride powders are not obviously crystallized within the synthesis temperature of 1400℃, and they belong to amorphous state. The crystalline polarmer of silicon nitride powders is not obvious within the temperature range of 1400℃ to 1500℃. Under the reaction temperature of 1500℃, silicon nitride powders present obvious crystal forms, which are α-Si3N4. The crystals of silicon nitride powders generated at 1500℃ are more obvious, and the grain sizes are relatively uniform. The particle size is 20nm~50nm, and the particle shape is mellow. （4）The density of the samples after sintering is higher, and the relative density is more than 0.98. Therefore, the densification processes of each group of samples have been basically completed at their sintering temperatures respectively. （5）The fracture toughness decreases with the reduction of sintering aids, while the hardness gradually increases. Under the same contents of sintering aids, the fracture toughness decreases with the increase of aluminium oxide,

and the Vickers hardness is enhanced. （6）Under the sintering temperature of 1500℃, when the contents of sintering aids are 6%, the components sintered are the two phases of α and beta, and the comprehensive performance of hardness and fracture toughness is favorable. （7）When the content of the added nanometer Si3N4 powders is 4%, the density, hardness and fracture toughness of the sintered components are preferable. （8）As can be seen from the friction and wear skeleton map, the depth and width of the worn volume decrease with the reduction of the sintering aids. Therefore, the wear resistance of the sample is enhanced with the decrease of the contents of sintering aids. The shaping of the material is favorable as observed from the boundaries on both sides of the scratch. N-P03 Piezoelectric Properties of (K,Na)NbO3 Ceramics Sintered at Low-Temperature under Reducing Atmosphere JungHwan Kim1, Jeong-Seog Kim1, Seung-Ho Han2, Hyung-Won Kang2, Hyeung-Gyu Lee2, Chae-Il Cheon1 Hoseo University1 Korea Electronics Technology Institute2

Piezoelectric ceramics are widely applied in many electronic devices such as precise actuators and various sensors. In recent years, lead-free piezoelectric ceramics have been developed in order to replace Pb-based piezoelectric ceramics due to an environmental issue. (K,Na)NbO3 (KNN) is one of the potential candidates for a lead-free piezoelectric ceramic. Low-temperature sintered ceramics is required for applications of multilayered piezoelectric actuators, piezoelectric MEMS devises and so on. To reduce manufacturing cost of multilayered actuators by replacing an expensive noble metal inner electrode, Ag/Pd with base metals such as Ni and Cu, piezoelectric ceramics should be sintered in low-oxygen partial pressure. KNN-based ceramics have been successfully prepared in reducing atmosphere, but sintered at temperature over 1000oC. In this work, KNN-based ceramics were manufactured at sintering temperature around 900oC under reducing atmosphere such as nitrogen and mixture of nitrogen and hydrogen gas. Na2CO3 and/or CuO were added to decrease the sintering temperature. Densification and microstructure development were investigated. Insulation resistances, dielectric properties and piezoelectric properties were measured in samples sintered in various atmospheres. Published only Domain Configuration and Thickness-dependent Properties in (K0.48Na0.52)(Nb0.95Sb0.05)O3- Bi0.50(Na0.82K0.18)0.50ZrO3 Lead-Free Piezoceramics Yalin Qin1, Jialiang Zhang2, Chaojing Lu1, Shujun Zhang3,4 1. College of Physics; Key Laboratory of Photonics Materials and Technology in Universities of Shandong, Qingdao University, Qingdao 266071, Shandong, P. R. China 2. School of Physics; State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, P. R. China 3. Materials Research Institute, Pennsylvania State University, Pennsylvania 16801, USA 4. Institute for Superconductor and Electronic Materials; Australia Institute of Innovative Materials, University of Wollongong, Wollongong, NSW 2500, Australia

The piezoceramics, which can make transitions between mechanical energy and electric energy, are usually used in transducers. For different application purposes, the size of the piezoceramics may be different and the thickness

may affect their electromechanical, dielectric and piezoelectric properties. (K0.48Na0.52)(Nb0.95Sb0.05)O3- Bi0.50(Na0.82K0.18)0.50ZrO3(KNNS-BNKZ) piezoceramics are recently reported as promising lead-free materials which possess good piezoelectricity that comparable with PZT. In view of the application in transducers, the thickness-dependency of the electromechanical and dielectric and piezoelectric properties in KNNS-BNKZ piezoceramics is worth further investigating. In this work, we prepared 0.9625(K0.48Na0.52)(Nb0.95Sb0.05)O3-0.0375Bi0.50(Na0.82K0.18)0.50ZrO3 (KNNS0.04-0.0375BNKZ) ceramics by conventional solid-state reaction method. Piezoelectric constant d33* measured under large signal was found as high as 547 pm/V. The average grain size is smaller than 5 μm, which demonstrates the KNNS0.04-0.0375BNKZ ceramics are fine-grained. The domain configuration was observed on polished and acid-etched face. It was found that before poling the domain patterns contain many watermarks and after poling they disappear a lot and make the domain patterns become simple. Thick samples were poled and cut into thinner samples with different thickness, and their thickness vibration electromechanical coupling factor kt, dielectric properties, d33*, d33 and ferroelectric hysteresis loop were measured. It was found kt, dielectric properties and d33* almost keep unchanged, while d33 and the remnant polarization Pr decrease when the sample thickness decreases. Besides, as the P-E loops becomes more and more compressed when the sample thickness decreases, the average coercive electric field Ec keeps almost unchaged, while the internal bias electric field Ei increases. The compressed P-E loops and the increased Ei demonstrate the clamp effect become obvious when the sample thickness decreases, and the domain switching become harder especially when the external electric field is not very high, which results in the decrease of d33 measured under small signal in thinner samples. However, when measured under large signal, the clamp effect seems being restrained, so that the d33* keeps almost unchanged when the samples become thinner. The results demonstrate that the KNNS0.04-0.0375BNKZ ceramics with fine grains are promising for transducer application. Structural Rearrangement of Barium Dititanate during Solidification Process Xuan Ge Shanghai Jiao Tong University Barium dititanate is a new lead free ferroelectric material found in BaO-TiO2 system. This material have a good ferroelectricity with a high curie point. According to experimental and simulative result, the material have an excellent optically nonlinearity, dielectric properties of high temperature and piezoelectricity etc. BT2 is a thermodynamically metastable phase when below 1200oC, have the tendency to decompose into BaTiO3 and Ba6Ti17O40, but has a strong kinetically stable when below 1100oC. As this material have a narrow thermodynamic stable range, so it’s hard to get pure barium dititanate material by conventional solid state sintered. Currently, the main method to prepare barium dititanate is growing out from melt, thus, the research about phase evolution and microstructure variation of barium dititanate during solidification process is helpful and benefit to obtaining better performance barium dititanate materials. The project was conducted based on aerodynamic levitation containerless melting method and X-ray diffraction derived from Synchrotron Rodiation. The specimen used in this experiment are BaCO3 and TiO2 powders, which were stoichiometrically weighted in the composition of BaTi2O5, mixed completely and Preliminary sintered in 1000oC. The aerodynamic levitation furnace employs conical nozzle levitation and uses aerodynamic force provided by oxygen flow to maintain of position solid and liquid specimens from room temperature to high temperature (2000oC). A 100W CO2 laser was employed to heat the specimen to desired temperature and controlled the heating and cooling rate. A CCD camera was used to obtain specimen view during melting and

cooling process. A optical pyrometer was used to recorder the temperature of specimen, and gave T-t curves after experiment. The aerodynamic levitation furnace was assembled on a two-axis translation stage to realize precise positioning of the specimen in the synchrotron radiation X-ray beam. The X-ray synchrotron experiment was carried out at beam line BL13W1 of Shanghai Synchrotron Radiation Facility (SSRF). The diffractive experiment employed high energy X-rays (30.5KeV, 0.040667nm) to provide a sufficiently scattering range and to reduce sample absorption as well as multiple scattering for both melt and crystal of barium dititanate above and below the melting point, the diffraction beam was detected using a Si flat-panel X-ray image plate, the specimen and optical path is under the condition of air. The X-ray illumination modes used in the experiments is X-ray beam partially intercepted by top of the specimen, which will ensure temperature uniformity in diffraction region. Diffraction intensities I(q) were extracted from integrating image plate data using fit2D software. These data were corrected for scattering from the air and geometry shape of specimen. After correcting for polarization, absorption, multiple scattering and Compton scattering, the S(q) could be obtained. Different phase and microstructure of barium dititanate were obtained in different cooling rate during solidification process. In our experiment, we observed that when the cooling rates over 80K/s，amorphous barium dititanate can be formed, at somewhat lower cooling rate the β-barium dititanate, which belongs to Pnma space group, will form directly from melt, while the cooling rate is less than 20K/s，only γ-barium dititanate (C2) can be formed. According to the X-ray synchrotron radiation result of barium dititanate melt, the first peak is near 20 nm-1, which revealed intermediate-range order, similar to many other network liquids. With the temperature decreasing, the first peak moved to lager Q, when the temperature of melt was 2000 oC, Q is equal to 19.3 nm-1; while under the condition of supercooling (700 oC) Q is 19.8 nm-1, which is the same to amorphous solid state. From the diffractive result we can also obtained that the coordination numbers became less with temperature decreasing. From SEM result, we can observed the β-barium dititanate grown like lath from the bottom of specimen to top under a faster cooling rate, the grown direction is preferred b-axis, which can be confirmed by XRD, with the cooling rate lower, γ-barium dititanate will occurs between lath crystal and lath crystal. However, if the cooling rate is too high, the β-barium dititanate’ preferred growth direction will changed. The first peak in the diffractive pattern represents Ti-O structure. According to others literatures, different phase of barium dititanate have different Ti-O band length and Ti-O[x] polyhedral, in the γ-barium dititanate, the length of Ti-O is near 20 nm and coordinate are 5~6; in the β-barium dititanate, the Ti-O bond length is near 19.8 nm and coordinate are 5; in the amorphous state, the bond length is 19.2nm and coordinate are 4~5. Based on this result, we think that in high temperature the structure of Ti-O polyhedral in melt is near γ-barium dititanate, however, under the supercooling state the structure of melt is near amorphous state, that to say, in the cooling process, the melt structure took place an rearrangement. Effects of Additives on Microstructure of Pressureless Sintering Al2O3 Ceramics Xiao-min Wang1, Bing-jun Wang1, Pei-qing La2 1. School of mechanical engineering, Qinghai University 2. Provincial Department of State Key Laboratory to Build Advanced Processing and Reuse of Non-ferrous metals, Lanzhou University of Technology

The effects of the amounts of MgO-SiO2-TiO2-Y2O3 composite additives as sintering aids on phase formation, sintering behavior, micro-structure and fracture conditions of Al2O3 ceramic were studied, which was prepared by the pressureless sintering and analyzed by the X-ray diffraction(XRD) technique and the field emission scanning electron microscope(FESEM). It was found that liquid and solid solution were generated in the grain boundary of samples at 1650℃. The result that liquid phase can be regarded as the ‘vessel’ in the samples, which advantageous

to the grain boundary diffusion and migration. Fracture mode of sample A was predominantly trans-granular fracture mode of mixed fracture mode and obvious cleavage steps and a small amount of tearing area were observed on the fracture surface. Whereas, compared with sample A, sample B had a well-developed grains and homogeneous of grain growth, but the dominant inter-granular fracture was occured. for various reasons weakened grain boundary. In addition, the higher mass fraction of additives changed growth habit of the individual Al2O3 grains, so grains grew up to platelike crystal which in favour of the fracture toughness of materials of sample B. In a word, adding the additives to make materials densifying and get a fine micro-structure.