The influence of a powder processing technique on chemical homogeneity and the diffuse phase transition behaviour of Ba0 9Ca0 1TiO3 ceramics

Abstract

Ba0.9Ca0.1TiO3 ceramics have been fabricated using powders obtained by calcining mixtures of (i) BaCO3, CaCO3 and TiO2 and (ii) Ba0.9Ca0.1CO3 and TiO2. The precursor Ba0.9Ca0.1CO3 was prepared by a wet technique to ensure homogeneous mixing of Ba and Ca ions at the atomic level. DTA analysis of solid state thermochemical reactions in the two types of mixtures shows that the temperature of reaction completion is 140 degrees C lower for the mixture containing the precursor carbonate solid solution. XRD results indicate better chemical homogeneity for powders obtained by the new route. A powder diffraction pattern for Ba0.9Ca0.1TiO3 has been theoretically computed assuming partial infstitution of Ba2+ by Ca2+. The theoretically predicted intensities are in good agreement with those experimentally observed for powders prepared by the precursor route only. Better chemical homogeneity with respect to the distribution of Ca2+ ions leads to more pronounced diffuse phase transition in Ba0.9Ca0.1TiO3 ceramics. © 1989 IOP Publishing Ltd.