Enhanced piezoelectricity and excellent thermal stability in modified BiFeO3–PbTiO3-based high-temperature piezoelectric ceramics

Ferroelectric ceramics possessing excellent piezoelectricity and high-temperature stability simultaneously are significant for sensor and actuation applications in severe environment such as extraterrestrial exploration and petroleum extraction. Herein, a novel (0.735−x)(Bi_0.972La_0.028)FeO₃–0.265PbTiO₃–xBa(Zr_0.2Ti_0.8)O₃ (abbreviated as (0.735−x)BLF–0.265PT–xBZT) was reported to own excellent piezoelectric coefficient d₃₃ value of ~ 394 pC/N with good temperature stability and high Curie temperature T_C value of ~ 445 °C, simultaneously, at x = 0.14, which is just located at the tetragonal (T)-rich side of rhombohedral (R)-T morphotropic phase boundary (MPB). It reveals that the compositions undergo an obvious phase from R phase to T phase via an R–T MPB, and finally to the coexistence of T and pseudo-cubic (PC) phases, which is found to be accompanied by the normal-relaxor ferroelectric transformation. The significant enhancement of the piezoelectric activity in x = 0.14 sample can be attributed to synergistic effect of R–T MPB and the normal-relaxor ferroelectric transformation, leading to the significantly enhanced domain switching although the sample exhibits a relatively large T distortion of ~ 1.039. In addition, the large tetragonality of T phase allows the sample to maintain high T_C value. The present work provides a guideline for the subsequent design of BF–PT-based high-temperature piezoelectric ceramics.