Stable piezoelectric property of modified BiFeO₃–BaTiO₃ lead-free piezoceramics

Perovskite-structured 0.696BiFeO₃–0.014Bi(Zn_1/2Ti_1/2)O₃–0.29BaTiO₃ (BF69.6–BZT1.4–BT29) lead-free piezoceramics with various MnO₂ addition were prepared using a refined solid state reaction electroceramic processing. Powder X-ray diffraction measurements showed their crystallographic structure being of rhombohedral structure and scanning electron microscopy observations revealed that MnO₂-doping enhances ceramic microstructure grain size growth. In contrast to BF–BT ceramics, low dielectric loss ceramics were obtained with combined strategies of refined electroceramic processing, Mn-doping and adding BZT third member. A good combination of ferroelectric and piezoelectric property was obtained in the 0.22 and 0.26 % in weight MnO₂-doped BF69.6–BZT1.4–BT29 coarse-grained ceramics and discussed in relation to microstructure grain size effect and point defect effect. Excellent time and thermal aging stabilities of piezoelectric constant d ₃₃ were also experimentally demonstrated and argued resulting from the feature of higher ferroelectric Curie temperature (T _C ) and no ferroelectric–ferroelectric structural phase transition below T _C of BF–BZT–BT system.