Effect of HfO2 content on the microstructure and piezoelectric properties of (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

(Bi0.5Na0.5)0.94Ba0.06TiO3–xHfO2 [BNBT–xHfO2] lead-free ceramics were prepared using the conventional solid-state reaction method. Effects of HfO2 content on their microstructures and electrical properties were systematically studied. A pure perovskite phase was observed in all the ceramics with x=0–0.07 wt%. Adding optimum HfO2 content can induce dense microstructures and improve their piezoelectric properties, and a high depolarization temperature was also obtained. The ceramics with x=0.03 wt% possess optimum electrical properties (i.e., d33~168 pC/N, kp~32.1%, Qm~130, εr~715, tan δ~0.026, and Td~106 °C, showing that HfO2-modified BNBT ceramics are promising materials for piezoelectric applications.