Powder Characteristics•At least include: chemical composition (major component & impurities), phase, particle size & distribution, surface area, density, porosity and pore size distribution, shape/ morphology, etc., will affect particle behavior, e.g. packing characteristics, rheology, surface characteristics, adsorption, particle strength etc..

•terminology: powder, particle (primary, secondary), colloid, agglomerate (soft), aggregate (hard agglomerate), granule, crystallite; (slightly different meaning of each word)

•Either single particle or particle system•Isotropic versus anisotropic property

Che5700 陶瓷粉末處理

In general:

<1 μm – colloids; >44 μm – granule

Granular: if gravity force important; colloid: gravity force insignificantPowder: surface force also important

• Hard agglomerate: primary chemical bonds formed by reaction or sintering• Soft agglomerate: relatively weak bonds, such as electrostatic, magnetic, Van der Walls, capillary adhesion etc.• Relative force between inertia force and surface force – granular system (gravitational force dominant); powder system; colloidal system (surface force dominant); surface force will be affected by environment including surfactnts;

Basic Definitions

Chemical Composition and Phases

•Bulk chemical analysis: (a) wet method – e.g. gravimetric, titration, colorimetric; (b) instrumental method – spectroscopic (AA, ICP-AES, etc.); •Major, minor, and trace components: different techniques, different easiness.

•Phase analysis: XRD, microscopy

•Surface analysis: focus on surface composition (ESCA, etc.)

•Thermochemical & thermophysical analysis:

Che5700 陶瓷粉末處理

Single particle and particle system

discussion: particle size (1st one largest), reflect on its bulk density (lowest)

From JS Reed,2nd ed.

Note: CO2, SO3 indicating incomplete calcination for (BaO+ SrO)/ (TiO2): 2nd & 3rd data >1.0 affect fired density & dielectric constant

PCE = pyrometric cone equivalent index

MBI: methyl blue index (adsorption quantity indicate surface areaMOR= modulus of rupture

From JS Reed, 2nd ed.; every method has its limits and advantages

Diffuse Fourier transform infared spectrum (DFTIR)

Oxygen Content in Oxides

•Taken from APL, 58(22), 2506, 1991

• As a semiconductor, oxygen content in oxide will affect its behavior as n or p type material, may require measurement, e.g. ZnO, SnO2, In2O3, etc. different processing different oxygen vacancy

•Technique used here: EPMA, use 4Kev electron beam, sample: sputtered tin oxide film, film electrical resistance should <10-4 -m; use EDS to get data. Factors influencing results: film thickness, surface roughness, In will absorb emission from oxygen;

Che5700 陶瓷粉末處理

Conclusion: high oxygen pressure high oxygen content in film high carrier conc. (excess oxygen in film)

Phase Analysis

•XRD: only for crystalline materials, its quantity better >5%, otherwise difficult;

•qualitative: compare with standard pattern (e.g. from ASTM); better check for three major peaks •Quantitative: (a) internal standard: add one material with clear peak (non-interfering), get calibration curve; (b) assume all crystalline materials, only two phases, x = Ia/(Ia + Ib)

•ED: electron diffraction, for very small region, often associated with TEM analysis

Che5700 陶瓷粉末處理

roughly, detection limit 5%, with better equipment may be down to 1%

From JS Reed,2nd ed.

High resolution TEM, for small region structure and morphology (from 楊建民博士論文 (顏富士教授指導 ))

Electron diffraction can also provide phase information, in association with EDS energy dispersive spectroscopy to get information on composition (from 楊建民博士論文 (顏富士教授指導 ))

Taken from 微電子材料與製程 , p.470 (common analysis used in microelectronics)

Basic Concepts of Analysis

•To use optical instrument to deviate or focus energetic particles (visible light, electrons, ions, X-rays) • interaction with samples • to generate secondary particles (visible light, secondary electrons, backscattered electrons, Auger electrons, photo-electrons, backscattered ions, fluorescent light, etc)• detect its spectroscopy, mass, energy or image

EPMAElectron probe for microanalysis

Taken from 微電子材料與製程 , p.484 ( 謝詠芬 , 何快容 )

Kα: from neighboring levels; KLL: Auger electrons

Taken from 微電子材料與製程 , p.472-473

Surface Analysis

Che5700 陶瓷粉末處理

Thermal Analysis

Che5700 陶瓷粉末處理

•Include:

• TGA: thermogravimetric analysis: weight loss• DTG: differential TGA (differentiate previous curve)• DTA: differential thermal analysis: temperature difference• DSC: differential scanning calorimetry: heat change• TMA: thermo-mechanical analysis: expansion or contraction effect

• Can operate under different atmosphere, different heating rate

system: BaCO3 + TiO2; 830, 990oC :BaCO3

structural transition; 1190, 1257oC: BaCO3 decomposition reaction, & subsequent formation of Ba2TiO4 and then BaTiO3