Phase transitions and electrical properties of (Na_(0.5)K_(0.5))NbO3-Bi(Sc_(0.5)Fe_(0.5))O3 lead-free piezoelectric ceramics

摘要

Lead-free ceramics (1-x)(Na_(0.5)K_(0.5))NbO_(3-x)Bi(Sc_(0.5)Fe_(0.5))O3 (KNN-BSF, x = 0-0.08) were synthesized by conventional solid-state sintering. A morphotropic phase boundary (MPB) is formed in the ceramics near x = 0.01-0.02 at room temperature by X-ray analysis. Dielectric temperature spectra indicate the existence of two dielectric anomalous peaks, which correspond to orthorhombic-tetragonal (Tot) and tetragonal-cubic (T_C) transitions. The ceramic with x = 0.0125 near the MPB exhibits the following optimal electrical properties: P_r = 33.9 μC/cm~2, E_c = 18.1 kV/cm, d_(33) = 255pC/N, k_p = 0.44, and T_C = 372°C.