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(Hf0.05Ti0.95)O3)-x(Bi0.2Sr0.7)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 Tf 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.