Dielectric properties of (Ba0.95Ca0.05)(Ti1−yCay)O3−yceramics

Abstract

Calcium doped barium titanate ceramics with composition (Ba_0.95Ca_{0. 05}) (Ti_1−yCa_y)O_3−y prepared by a liquid mixing technique were used to measure the dielectric properties. The pure barium titanate and lightly-Ca-doped materials obey a Curie Weiss law when the temperature is above the Curie temperature. It has been found that the average cubic-tetragonal phase transition temperature moves downward when the octahedrally-coordinated Ca concentration increases, and heavily-Ca-doped barium titanate ceramics show relaxor behavior with a diffuse phase transition characteristic (DPT). Above the average transition temperature T_av the dielectric properties for heavily doped materials do not obey the Curie Weiss law, but can be described by a quadratic relation over a wide range of temperature. Experiments have shown that there exists an extra K(T) peak attributable to the existence of separate microregions of Ba_0.95Ca_0.05TiO₃ in a matrix of (Ba_0.95Ca_0.05) (Ti_1−yCa_y)O_3−y (where y ≤ 2%).