Deciphering the leakage conduction mechanism of BiFeO 3–BaTiO 3 lead-free piezoelectric ceramics

BiFeO3-BaTiO3 based piezoelectric ceramic is a kind of high-temperature lead-free piezoelectric ceramic with great development prospects due to its high Curie temperature TC and excellent electrical properties. However, the large leakage current limits its performance improvement and practical application. In this work, DC (direct current) test, AC (alternating current) impedance and Hall tests were used to investigate the conduction mechanisms of 0.75BiFeO3-0.25BaTiO3 ceramic over a wide temperature region. In the range of RT−150 °C, Ohmic conduction plays a predominant effect, and the main carriers are p-type holes with the activation energy (Ea) of 0.51 eV. When T > 200 °C, the Ea value calculated from AC impedance and Hall data is 1.03 eV with oxygen vacancies as a cause of high conductivity. The diffusion behavior of the thermally activated oxygen vacancies is affected by crystal symmetry, oxygen vacancy concentration and distribution, dominating the internal conduction mechanism. Deciphering the conduction mechanisms over the three temperature ranges would pave the way for further improving the insulation and electrical properties of BiFeO3-BaTiO3 ceramics.