High piezoelectric coefficient and thermal stability of BKT-BFPT ceramics with <i>ex situ</i> high depoling temperature at 520 °C

The in situ and ex situ temperature dependence of dielectric and piezoelectric properties of 0.1(Bi0.5K0.5)TiO3-0.6BiFeO3-0.3PbTiO3 (BKT-BFPT) ceramics were characterized, and related mechanisms were studied. The tetragonal distortion, Curie temperature Tc, depoling temperature Td, and piezoelectric coefficient d33 of BKT-BFPT are 0.06, 545 °C, 520 °C, and 205 pC/N, respectively. The in situ piezoelectric coefficient variation of BKT-BFPT ceramics from room temperature to 280 °C is only 10%, being 1/5 and 1/10 those of 0.36BiScO3-0.34PbTiO3 and Pb(Zr0.52Ti0.48)O3 ceramics. The better dielectric and piezoelectric thermal stabilities are owing to the temperature insensitive domain texture of BFPT-BKT ceramics due to their large lattice distortion. Resistivity results reflected that the higher depoling temperature derived from the ex situ measurement than that from the in situ test results from the high-temperature conductivity.