Conduction properties of acceptor-doped BaTiO₃–Bi(Zn_1/2Ti_1/2)O₃-based ceramics

A series of acceptor-doped ceramics based on the solid solution, (1-x)BaTiO₃–xBi(Zn_1/2Ti_1/2)O₃ (BT-BZT), where x = 0.1, 0.2, 0.3, 0.4, were prepared via solid-state synthesis to investigate the effect of doping and BZT content on conduction properties. Impedance spectroscopy measurements showed an increase in conductivity through acceptor doping with Mg on the Ti-site (\({\text{Mg}}_{{{\text{Ti}}}}^{^{\prime\prime}}\)). Ceramics of the composition, 0.80BaTiO₃–0.20Bi(Zn_1/2Ti_1/2)O₃ with 3 mol% \({\text{Mg}}_{{{\text{Ti}}}}^{^{\prime\prime}}\), showed the highest conductivity in this study at 1.28 mScm⁻¹ (~ 600 °C), an order of magnitude improvement over the stoichiometric composition. Variable pO₂ impedance measurements revealed p-type conductivity in the grain while EMF measurements showed that above ~ 550 °C, ions are the dominant charge carriers (transference number, t_i = 0.91 at 735 °C). Similarly, all 3 mol% Mg-doped compositions above x = 0.1 were primarily ionic conductors with transference numbers above t_i = 0.79 (735 °C). X-ray diffraction data showed a pseudocubic primary phase for all samples with evidence of additional impurity phases accompanying samples with 3 mol% \({\text{Mg}}_{{{\text{Ti}}}}^{^{\prime\prime}}\) or greater.