Lanthanum‐Induced Morphotropic Phase Boundary in BiFeO3–BaTiO3‐Based Lead‐Free Piezoelectric Ceramics

Abstract

0.71Bi1.05(1−x)LaxFe0.98Ga0.02O3–0.29BaTiO3 + 0.1wt%MnO2 ceramics are fabricated via a traditional solid‐state reaction route. Rietveld refinement analysis of X‐ray diffraction data shows that all the studied ceramics consist of rhombohedral and tetragonal phases. The La‐free samples are dominated by rhombohedral phase, the proportion of which, however, gradually decreases with the addition of La. And in 0.005 ≤ x ≤ 0.02, the ceramics have approximately equal proportions of rhombohedral and tetragonal phases, showing the characteristics of typical morphotropic phase boundary (MPB). The optimal piezoelectric properties (d33 = 178 pC N−1 and kp = 0.31) are achieved at x = 0.005, owing to the MPB. A more apparent relaxor behavior is found to be induced with the addition of La. Furthermore, the ceramics also exhibit good insulation properties and high‐temperature stability of piezoelectric properties, which is very important for practical uses, especially for those in high‐temperature environments.