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

Perovskite-structured 0.696BiFeO3–0.014Bi(Zn1/2Ti1/2)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 d33 were also experimentally demonstrated and argued resulting from the feature of higher ferroelectric Curie temperature (TC) and no ferroelectric–ferroelectric structural phase transition below TC of BF–BZT–BT system.