Influence of Core‐Shell Grains on the Internal Stress State and Permittivity Response of Zirconia‐Modified Barium Titanate

Abstract

BaTiO 3 modified with grain‐boundary resident ZrO 2 (≤ 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(Ti 1− x Zr x )O 3 ) 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 BaTiO 3 . 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.