International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009 Special Issue-1, June-2015

Structural And Magnetic Study Of Nickel Doped Nanocrystalline Z Hexaferrite With Increase In Temperature

145

STRUCTURAL AND MAGNETIC STUDY OF NICKEL DOPED NANOCRYSTALLINE Z HEXAFERRITE WITH INCREASE IN

TEMPERATURE 1SUHASINI M. DAFE 2S. R. THAKARE 3MAHESHKUMAR Y. SALUNKHE, 4FARHEEN I. BAIG

123Institute of Science, Nagpur, India.

4 Shivaji Science College, Nagpur, India. Email: suha_dafe@rediffmail.com

Abstract— The synthesis of nanocrystalline Z-type Hexaferrite Sr3Ni2Fe24O41 powders by conventional ceramic method at two different temperature 600°C and 800°C has been investigated and consequently, low temperature sintering and good magnetic properties were achieved. The phase identification of the sample was carried out by XRD. The microstructure of the sintered sample was studied by SEM indicates that the ferrite formed are hexagonal shape having crystalline size in the range of 90nm to 100nm. Magnetic properties were discussed by M-H curve using Hysteresis loop tracer and it is found that with increasing in sintering temperature coercivity as well as retentivity of Hexaferrite increases whereas saturation magnetization remains same.

Index Terms— Hexaferrite, ceramic, XRD, microstructure, magnetization.

I. INTRODUCTION

A ferrites nanomaterial attends great importance due to their scientific and industrial applications such as notebook computers, cellular phones, inductor cores, UHF communication devices, electromagnetic wave absorber etc. The scientist looking towards reducing the size of the devices which can be achieved by miniaturizing the ferrite components. Preparing hexaferrite in the nano range not only reduces the size of the component but improves their properties to great extent. Magnetic properties of the ferrite nanoparticles are fundamentally different than that of the bulk capture a great interest of the researchers [1].

A high density recording media is one of the most important applications of strontium hexaferrite. Media noise is the major issue in high density recoding media which results from coupling between the magnetic grains. This could be avoided by using small grain size in the nano range. The main application of ferrite is multilayer chip inductors (MLCI) which are important passive surfaces

mounting devices (SMD) in modern electronic industry [2] Z hexaferrite are considered to be promising materials for fabrication of MLCI because of its performance in high frequency region [3-5]. But the possible formation temperature of Z hexaferrite is more than 1250 C However, MLCI fabrication requires ferrites that are sintered at a relatively low temperature of 850–950°C. Ceramic method is the standard method for the preparation of hexaferrite but it required very high temperature to form single phase Z hexaferrite. Preparing nanocrystalline Z hexaferrite by ceramic method at such a high temperature is tough as agglomeration go on with increasing temperature. Here we tried ceramic method using oxalates to obtained nanocrystalline Z hexaferrite at relatively low temperature less than 900°C and studied its structural and magnetic properties.

II. MATERIAL SYNTHESIS

The ferrite samples Sr3Ni2Fe24O41 studied in the present investigation was prepared by conventional ceramic method. Initially, high purity Strontium Oxalate (SrC2O4), Iron Oxalate (C2FeO4), and Nickel Oxalate (C2NiO4) were mixed together in stoichiometric.

The resulting mixture then crushed in agate mortar for 2 hr to form homogenous mixture. The mixture was then fired at about temperature for 12 hr respectively.

COCOOFeNiSrNiOCFeOCSrOC 38202243 2412423424242

The phase characterization was analyzed using Philips PW-1710 X-ray diffractometer (XRD). SEM was used to observe the microstructure of the fracture surface of the samples. The magnetic properties were studied by hysteresis loop tracer.

III. RESULTS AND DISCUSSION

International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009 Special Issue-1, June-2015

Structural And Magnetic Study Of Nickel Doped Nanocrystalline Z Hexaferrite With Increase In Temperature

146

A. Phase formation and cell parameters

Fig 1. Diffraction pattern of Nano ferrite prepared at 600oC.

Fig 2: shows diffraction pattern of Nano ferrite prepared at 800oC

The phase composition of ferrite powder sintered at 600°C and 800°C, respectively, were studied by XRD. It was found from the diffractogram that the peaks correspond to hexaferrite phase which confirms the formation of Nano nickel hexaferrite. Initially on firing at 600°C, the completeness of Z-type hexaferrite observed while increasing the firing temperature to 800°C Z-type ferrite was detected as a main phase. The peak width decreases with increasing temperatures as a result of growth of crystals and production towards larger cluster. Lattice parameter of the compound fired at 600°C and 800°C were found to be a = 5.941, c = 52.439 and a = 5.935 , c = 50.691respectivelly which resemble with standard data a = 5.88 and c = 52.31. Lattice parameters found to be decreases with increasing temperature. Hexaferrite Sample fired at 600°C temperature exhibit higher lattice parameters due to

the presence of defects and impurities which might be introduce during sample preparation. Increasing in the firing temperature to 800oC leaded to increase the crystal growth by removing impurities and decreasing the defects in crystallites. The average crystallite size was calculated from the most intense peak using the Scherrer’s formula. The Crystallite size of the Z ferrite prepared at 600oCand 800oC are found to be 27.8nm and 38.9nm respectively. This shows that agglomeration takes place with increase in temperature. B. Grain morphology

SEM was used to observe the microstructure of the sintered samples at two different temperatures. The Sr-Z hexaferrite sintered at 600°C shown in the fig. 3. It indicates that Z-type ferrite particles are plates like

Position 2Theta]

20

30

40

50

60

70

80

90

Counts

0

5

1000

Position [°2Theta

2 3 4 5 6 7 8 9

Counts

0

2

4

6

International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009 Special Issue-1, June-2015

Structural And Magnetic Study Of Nickel Doped Nanocrystalline Z Hexaferrite With Increase In Temperature

147

structure and an average particle size of 120-135nm. This structure was found more complicated. SEM of the Sr-Z hexaferrite sintered at 800°C shown in the fig. 4 indicates that Z-type ferrite particles are hexagonal shape and an average particle size of 85-100 nm. This structure shows the regular arrangements of the particles. This indicates that homogenous crystal growth observed with increase in temperature.

Table I. LATTICE CONSTANTS A, C, CRYSTALLITE SIZE, GRAIN SIZE, MAGNETIZATION , COERCIVITY AND RETENTIVITY OF Sr3Ni2Fe24O41FIRED AT TWO DIFFERENT TEMPERETURE .

Parameters 600°C 800°C

A 5.941Å 5.935Å

C 52.439Å° 50.691Å

Crystallite size 27.8nm 38.9nm

Grain size 120-135nm 85-100nm

Coercivity 11.74 Oe 17.64 Oe

Retentivity 405.04mV 419.48 Gauss

Magnetic Saturation

983.68mV 983.68 Gauss

Fig.3. SEM images of Sr3Ni2Fe24O41 nano hexaferrite sample fired at 600°C.

Fig.4. SEM images of Sr3Ni2Fe24O41 nano hexaferrite sample fired at 800°C.

C. Magnetic characterization

Magnetic hysteresis loop measured at room temperature demonstrate that the sample are ferrimagnetic. The magnetic behaviour of nickel hexaferrite nanoparticles is very sensitive to the crystallite and particle size [6]. The hysteresis loop of both the sample is slim indicating soft magnetic behaviour. The coercivity value of the sample fired at 600°C and 800°C were found to be 11.74Oe and 17.64Oe respectively. These values are much smaller than that of the bulk Z hexaferrite [7, 8]. With increase in sintering temperature coercivity found to be increased. Increase in coercivity due to decrease in grain size particularly below single domain size. It was found that magnetic domains in magnetic crystals have a minimum size below which the magnetic materials cannot split up further into domains [9–11] and are called single domain particles. In a single-domain particle, all the spins are aligned in the similar direction and the particle is uniformly magnetized. Because there are no domain walls to move, the magnetization will be reversed through spin rotation rather than through the motion of domain walls. This results in increased in the

International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009 Special Issue-1, June-2015

Structural And Magnetic Study Of Nickel Doped Nanocrystalline Z Hexaferrite With Increase In Temperature

148

coercivity of the nanoparticles with decreasing grain size. The retentivity calculated of the sample sintered at 600°C and 800°C are 405.04 Gauss and 419.4Gauss respectively, which also shows increase in retentivity with increases in temperature. The saturation magnetization of sample fired at both the temperature are found to be same i.e. 983.68Gauss.

Fig 5. Variation of Coercivity with mag. field of sample heated at 600°C

Fig.6. Variation of retentivity with applied mag. Field of sample heated at 600° C

Fig.7. Variation of magnetic saturation with applied magnetic field of sample heated at 600°C.

Fig.8. Variation of Coercivity with mag. field of sample heated at 800°C

Fig. 9. Variation of retentivity with applied mag. Field of sample heated at 800° C

Fig.10. Variation of magnetic saturation with applied magnetic field of sample heated at 800C.

CONCLUSION

The experimental results presented in the study are intended to describe the effect of temperature on structural, morphological and magnetic properties of Sr-Z hexaferrite. From the XRD studies and SEM micrographs, we found that the nano size z-type ferrite formed in the range of 90-100 nm. The lattice

02468

10

12

14

16

18

20

0 100

200

300

400 Magnetic field

(Gauss )

Loop width x 2 mm

International Journal of Advances in Science Engineering and Technology, ISSN: 2321-9009 Special Issue-1, June-2015

Structural And Magnetic Study Of Nickel Doped Nanocrystalline Z Hexaferrite With Increase In Temperature

149

parameter found to be decreased with increase in temperature. From the hysteresis loop it was found that the magnetic properties of the ferrite such as coercivity and retentivity increases with increased in temperature whereas magnetic saturation shows no change with increase in temperature.

REFRENCES

1. Y. Wang, L. Li, Z. Yue, Z. Gui, IEEE Trans. Magn. 38 (2002) 1797.

2. H . Zhang, J. Zhou, Y.Wang, L. Li, Z. Yue, Z. Gui, J. App. Phys. 91 (2002) 5230.

3. X . Wang, L. Li, Z. Yue, S. Su, Z. Gui, J. Zhou, J. Magn. Magn. Mater. 246 (2002) 434.

4. Kamellia Nejati, Nejati and Tanaka, 1999).[ Tanaka T., IEEE Transactions on Magnetics 35 (1999) 3010-3012.

5. J.Y. Park, M.G. Allen, IEEE Trans. Magn. 34 (4) (1998) 1336.

6. H. Zhang, J. Zhou Zabihi Chemistry Central Journal 2012, 6:23.

7. ALI-SHARBATI , Digest Journal of Nanomaterials and Biostructures Vol. 6, No 1, January-March 2011, p. 187 – 198.

8. J. Xu et al. / Journal of Alloys and Compounds 509 (2011) 4290–4294.

9. Frenkel, J.; Doefman, J. Spontaneous and induced magnetisation in ferromagnetic bodies. Nature 1930, 126, 274–275.

10. Kittel, C. Theory of the structure of ferromagnetic domains in films and small particles. Phys. Rev. 1946, 70, 965–971.

11. Mørup, S.; Hansen, M.F.; Frandsen, C. Comprehensive Nanoscience and Technology; Andrews, D., Scholes, G., Wiederrecht, G., Eds.; Elsevier: Amsterdam, The Netherlands, 2011; pp. 437–491