INFLUENCE OF CORE SHELL GRAINS ON THE INTERNAL-STRESS STATE AND PERMITTIVITY RESPONSE OF ZIRCONIA-MODIFIED BARIUM-TITANATE

BaTiO3 modified with grain‐boundary resident ZrO2 (≤ 2 wt%) results in substantial chemical modification of the microstructure when sintered at 1320°C for 2 h. These modified regions were seen as core‐shell grains in the micro‐structure and were accompanied by an increase in the internal stress level. The shells had a variable composition (Ba(Ti1−xZrx)O3) and a tetragonal structure. An expansion mismatch between the core and the shell placed the core in compression resulting in a decrease in the lattice parameter and a pseudocubic structure with respect to the unmodified BaTiO3. The combination of core‐shell grains and increased internal stress resulted in an essentially flat permittivity response with temperature, a condition consistent with a distribution of Curie points within the ceramic. Copyright © 1990, Wiley Blackwell. All rights reserved