BaTiO₃-Ni複合セラミックスの焼結と誘電特性

抄録

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 ε_r′=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.