Enhanced Electric Field-Induced Strain Properties in Lead-Free BF-BT-Based Piezoceramics by Local Structure Inhomogeneity

The piezoelectric strain coefficient d₃₃* always deteriorates rapidly with increasing temperature, which is one of the technical bottlenecks restricting practical applications of piezoelectric ceramics at high temperatures. Herein, we successfully prepared (1 – x)­(0.7BFeO₃-0.3Ba­(Hf_0.05Ti_0.95)­O₃)-x(Bi_0.2Sr_0.7)­TiO₃ by the conventional solid-state method, which possessed a high piezoelectric strain coefficient of d₃₃* = 490 pm/V at 245 °C. In particular, d₃₃* is insensitive to the temperature range of 25 to 245 °C. Microstructure characterization and electrical performance measurements showed that the optimal piezoelectric strain coefficient and its excellent thermal stability are mainly attributed to combining freezing temperature T_f with polar nanoregions (PNRs). Piezoelectric force microscopy showed the relaxor behavior, and high-resolution transmission electron microscopy images of the Moiré fringe revealed the existence of PNRs. The conception and findings in this work will further push the practical application of BiFeO₃-BaTiO₃-based high-temperature piezoceramics.