Enhanced piezoelectric properties in coarse-grained 0.7Bi(Fe0.9985Mn0.0015)O3-0.3BaTiO3 ceramics

The lead-free BiFeO 3 -BaTiO 3 (BF-BT) based ceramics with large piezoelectric coefficient ( d 33 ) have been desired for promising applications in high-temperature fields. Herein, the 0.7Bi(Fe 0.9985 Mn 0.0015 )O 3 -0.3BaTiO 3 ceramics with different grain sizes are intentionally prepared by solid-state method, and a large d 33 (232 pC/N) and high Curie temperature T c (501 °C) are simultaneously achieved in the case of large grain size (>9 µm). X-ray diffraction and Rietveld refinement analyses indicate that these coarse-grained samples possess stronger rhombohedral distortion and enlarged lattice parameter compared to fine-grained samples, which make domain switching easier and give rise to the increase in strain. As a result, the piezoelectric and ferroelectric properties of such samples are significantly improved with increasing grain size from 3.05 µm to 9.07 µm. In addition, electric domain configuration and field-induced strain further prove that the strong piezoelectric response in coarse-grained samples is attributed mainly to enhanced non-180° domain mobility. This study reveals the origin of large piezoelectric response in coarse-grained BF-BT ceramics, and proposes an effective approach to improve the piezoelectric properties of BF-BT ceramics.