Electrical Properties of Polycrystalline Ceramic Insulators.
Final rept. 1 Apr 75-31 Jul 77,
FLORIDA UNIV GAINESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
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An attempt has been made to show the effect of microstructure on electrical properties in several types of idealized polycrystalline ceramic insulators. The concept of the path of microstructural change was used to vary hotpressing or sintering conditions to produce samples of Al2O3-porosity and Al2O3-SiO2 with systematically related microstructures. The most detailed quantitative microstructural study yet reported for a ceramic system was made on these samples. Information on volume fractions, surface area, curvatures and lengths of various features shows clearly that classifying specimens only on the basis of density and average grain size, as is commonly done, tends to lump together samples with very different microstructures, thus observing microstructure-porsity relations. Dielectric measurements on Al2O3-porosity specimens with similar densities and chemical compositions but different values for the quantitative microscopic variables reveal strong differences inconductivity, dielectric constant and dielectric loss behavior. A qualitative model involving bulk and grain boundary conduction is advanced to explain dielectric data obtained for a series of systematically related Al2O3-porosity specimens. A quantitative microscopic investigation of BaTiO3 microstructure to determine if the technique might be useful in understanding ferroelectric aging effects is disucussed in the second part of the report. Author
- Ceramics, Refractories and Glass
- Electricity and Magnetism