Enhanced dielectric and piezoelectric properties of Mn modified 0.65(Bi_0.95La_0.05)FeO₃-0.35Pb(Ti_1-xMn_x)O₃ ceramics

Piezoelectric ceramics of 0.65(Bi_0.95La_0.05)FeO₃-0.35Pb(Ti_1-xMn_x)O₃ (BLF-PTM) (x = 0, 0.01, 0.02, 0.03 and 0.04) were prepared by the conventional solid-state reaction method. X-ray diffraction analysis reflected that BLF-PTM ceramics showed pure perovskite structure with the coexistence of rhombohedral and tetragonal phases, and tetragonal distortion decreased slightly with Mn content. Dielectric and piezoelectric properties of BLF-PTM ceramics were enhanced obviously by Mn doping. The Curie temperature T _C, depolarization temperature T _d, dielectric constant ε _r (1 kHz), dielectric loss tanδ (1 kHz), piezoelectric constant d ₃₃, planar electromechanical coupling factor k _p and mechanical quality factor Q _m for BLF-PTM ceramics of x = 0.02 were 534, 475 °C, 230, 0.003, 100 pC/N, 0.29 and 560, respectively. The dielectric loss was reduced to one-sixth while piezoelectric constant was improved to one and half those of BLF-PTM ceramics without Mn modification. The depoling temperature was about 300 °C higher than that of Pb(Zr,Ti)O₃ (PZT) based ceramics. Our results indicated that BLF-PTM ceramics were promising candidates for high temperature piezoelectric applications.