Sintering and Dielectric Properties of BaTiO<sub>3</sub>-Ni Composite Ceramics

Abstract

BaTiO3-Ni mixed powders were sintered at 1300°C in Ar or air, and the sintering behavior and dielectric properties were investigated. The bulk density of sintered bodies was 95-99% of theoretical. BaTiO3-Ni composites were produced in Ar. When coarse Ni powder (4-7μm) and ultrafine BaTiO3 powder (0.02μm) were used, a large number of Ni particles were isolatedly dispersed in the BaTiO3 matrix. The dielectric constant increased remarkably with an increase in Ni content up to er′=11000 at 40vol% Ni according to the modified Maxwell formula. Although monolithic BaTiO3 sintered in Ar had a high dielectric loss owing to the formation of oxygen vacancies working as electron donor, BaTiO3-Ni composite had a low dielectric loss. This is because of the fact that a small amount of NiO dissolved into BaTiO3 and Ni ions worked as electron acceptor to compensate the charge of oxygen vacancies. Firing in air resulted in the oxidation of Ni to form BaTiO3-NiO composites with low dielectric constants and high dielectric losses.