Microstructures and Dielectric Properties of Fine-Grained BaTiO₃ Ceramics

Abstract

BaTiO3 powders of 0.2 µ m and 0.5 µ m particle size diameters were prepared by changing the calcination temperature of BaTiO3 synthesized by a hydrolysis method. Glass frit mainly consisting of SiO2 was added as a sintering aid. In the case of using 0.2 µ m powder, grains grew to 0.5 µ m in diameter at sintering. Ceramics exhibited no secondary phase caused by glass frit at the grain boundary and showed a large dielectric constant at the Curie temperature. On the other hand, in the case of using 0.5 µ m powder, grain size remained the same as the calcined powder size. Ceramics had a grain boundary layer of 1 nm thickness and showed stable temperature dependence of the dielectric constant. Ununiform lattice distortion, as calculated by the Hall method, was greater in the latter ceramics. It is considered that the ununiform lattice distortion was caused by the stress from the grain boundary layer, resulting in the lowering of the dielectric constant at the Curie temperature and the increase of the dielectric constant in the ferroelectric phase.