0.74BiFe1- x Ga x O3-0.26BaTiO3 高温无铅压电陶瓷的相变行为及电性能

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

摘要:

准同型相界（MPB）对提升压电陶瓷的压电性能具有重要的作用。BiFeO₃-BaTiO₃体系的准同型相界通常位于0.70BiFeO₃-0.30BaTiO₃组分附近。然而，对于BiFeO₃-BaTiO₃体系，BaTiO₃含量越高其居里温度越低。因此，在较低的BaTiO₃含量组分附近构建准同型相界是使其同时获得良好的压电活性和高居里温度的有效策略。采用固相法制备了0.74BiFe_1-xGa_xO₃-0.26BaTiO₃（x=0~0.05）系列无铅压电陶瓷，研究了Ga含量对其物相结构与电性能的影响。结果表明：随着Ga含量的增加，陶瓷样品从三方相逐渐向赝立方相转变。当x≤0.01，陶瓷样品为三方相结构；而当0.04≤x≤0.05，陶瓷样品为赝立方结构，在0.02≤x≤0.03形成了准同型相界（三方-赝立方）。另外，由于容忍因子的升高，该系列陶瓷的居里温度随着Ga含量的增加而略有降低。位于准同型附近的陶瓷样品表现出良好的压电活性和较高的居里温度。

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.