Dielectric properties of (Ba0.8−xBi0.2)(Zn0.1Ti0.9)O3 ceramics for high temperature applications

A number of Pb-free BaTiO₃ - Bi(Zn_1/2Ti_1/2)O₃ solid solutions have been studied by Huang et al.. 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°C 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 capacitor 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 investigated. The optimum compositions exhibited a relative permittivity in excess of 1150 and 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, an ionic conduction mechanism was suggested to be responsible for the resistivity at high temperatures.