Composition-Driven Phase Transition and Electrical Perfor-mances of 0.74BiFe1- x Ga x O3-0.26BaTiO3 High Temperature Lead-Free Piezoceramics

Abstract:

Morphotropic phase boundary (MPB) is very important for enhancing piezoelectric properties of piezoceramics. In general, the MPB of BiFeO₃-BaTiO₃ system ceramics locates near the composition of 0.70BiFeO₃-0.30BaTiO₃. However, higher content of BaTiO₃ will lead to lower Curie temperature of BiFeO₃-BaTiO₃ ceramics. Therefore, constructing an MPB for BiFeO₃-BaTiO₃ ceramics with lower BaTiO₃ content is a reasonable strategy to obtain both the good piezoelectric property and high Curie temperature. 0.74BiFe_1-xGa_xO₃-0.26BaTiO₃ (x=0~0.05) lead-free piezoceramics were fabricated by traditional sintering methods, and effect of Ga content on the structures and electrical performances was investigated. Results show that a composition-driven phase transition from rhombohedral (R) to pseudocubic (pC) is identified as x increases from 0 to 0.05. The ceramics show symmetries of R at x≤0.01 and pC at 0.04≤x≤0.05, and the MPB with R-pC coexistence is detected in the composition range of 0.02≤x≤0.03. The Curie temperature of the piezoceramics decreases slightly owing to increased tolerance factor t with the increment of Ga content. In particular, the high Curie temperature ~515 °C and improved piezoelectric property of piezoelectric coefficient d₃₃ of ~127 pC/N are obtained in the ceramics near MPB.