Enhanced strain and its temperature stability in BF-BT-based piezoelectric ceramics via Hf modification

The BiFeO 3 –BaTiO 3 piezoelectric ceramic possesses high Curie temperature, rendering it a promising candidate material for high-temperature piezoelectric actuators, yet the low strain and undesired temperature stability have to be resolved. In this study, the piezoelectric system 0.95(0.7BiFeO 3 –0.3BaTiO 3 )–0.05(Ba 0.6 Sr 0.4 )TiO 3 (BF–BT–BST) was probed with Hf modification. Results demonstrate that the introduction of Hf 4+ ions promotes the phase transition from the rhombohedral to the pseudocubic, leading to the formation of polar nanoregions (PNRs). With increasing Hf 4+ level, the freezing temperature gradually decreases from 297 °C to 31 °C, and Hf modification activates the activity of PNRs at room temperature, creating a more responsive relaxation state of PNRs to external electric fields. Consequently, the modification increases the strain up to 0.45 % and results in a good temperature stability of 17 % from 25 °C to 200 °C for the sample with 0.75 % Hf. The findings present an effective strategy for improving the strain and temperature stability in BF–BT–based piezoelectric ceramics.