High piezoelectric properties above 150 °C in (Bi0.5Na0.5)TiO3-Based lead-free piezoelectric ceramics

(Bi0.5Na0.5)TiO3–BaTiO3 lead-free piezoelectric ceramics exhibit excellent piezoelectric properties, but its piezoelectric property with high thermal stability is the major obstacle limiting the potential application. In this study, the KNbO3 (KN) was adopted to 0.875(Bi0.5Na0.5)TiO3-0.125BaTiO3 (BNT-12.5BT) by conventional solid-state reaction to enhance the piezoelectric properties in high temperature. The results of X-ray diffraction (XRD) indicate that KN has diffused into BNT-12.5BT lattices to form a pure perovskite structure and not exert a severe disturbance on the ferroelectric tetragonal lattice. The depolarization temperature Td is maintained at a high level. For piezoelectric properties, at KN modification x = 0.01, the piezoelectric coefficient (d33) increases to 147 pC/N from 135 pC/N for unmodified composition. Meanwhile, the d33 will increase to 187 pC/N until the depolarization temperature (185 °C) arrives, showing the excellent temperature stability of the piezoelectric properties to meet the actual demand. •New KNbO3-doped 0.875(Bi1/2Na1/2)TiO3-0.125BaTiO3 ceramics were fabricated.•The d33 value for the sample with 1.0 mol.% KNbO3 keeps around 147–187 pC/N until the temperature arrives to185 °C.•The steady lattice structure and ferroelectric order is contributed to the excellent thermal stability of piezoelectricity.