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

Solid solutions of BaTiO
₃
-Bi(Zn
_1/2
Ti
_1/2
)O
₃
were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO
₃
-0.2Bi(Zn
_1/2
Ti
_1/2
)O
₃
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-x
Bi
_0.2
)(Zn
_0.1
Ti
_0.9
)O
₃
ceramics where 0 ≤ x ≤ 0.08, as well as ZrO
₂
- and Mn
₂
O
₃
- 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.