High-K (Ba0.8Bi0.2)(Zn0.1Ti0.9)O3 ceramics for high-temperature capacitor applications

Solid solutions of BaTiO₃-Bi(Zn_1/2Ti_1/2)O₃ were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO₃-0.2Bi(Zn_1/2Ti_1/2)O₃ revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range of 100 to 350°C was also obtained. In this study, the effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation resistance for high-temperature applications. The dielectric response of (Ba_0.8-xBi_0.2)(Zn_0.1Ti_0.9)O₃ ceramics where 0 ≤ x ≤ 0.08, as well as ZrO₂- and Mn₂O₃- doped ceramics were studied. The optimum compositions exhibited a relative permittivity in excess of 1150 with a low loss tangent (tan δ <; 0.05) that persisted up to a temperature of 460°C. The temperature dependence of resistivity also revealed the improved insulation resistance of Ba-deficient compositions. Additionally, we suggest that an ionic conduction mechanism is responsible for the degradation of resistivity at high temperatures. The temperature coefficient of permittivity (τ_K) and the RC time constant were also investigated.