Microstructure and electrical properties of La2O3-doped Bi0.5(Na0.68K0.22Li0.1)0.5TiO3 lead-free piezoelectric ceramics

La2O3-doped Bi-0.5(Na0.68K0.22Li0.1)(0.5)TiO3 lead-free piezoelectric ceramics have been successfully prepared by conventional solid state method and the effects of La2O3 doping on microstructure and electrical properties of the ceramics were investigated. The X-ray diffraction patterns demonstrated all ceramics possessed pure perovskite structure with rhombohedral symmetry. The temperature dependence of dielectric constant and dielectric loss revealed two abnormal dielectric peaks of T-d and T-m, which implied that from room temperature to 500 degrees C all ceramics underwent two phase transitions which were from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric, respectively. It was also found that the transition temperature T-d decreased with the addition of La2O3. Diffuse phase transition and frequency dispersion of the dielectric constant were observed in all ceramics. Dielectric relaxor behavior obeyed the modified Curie-Weiss law. The results revealed that all samples had relaxor characteristics. In addition, for the ceramics with 0.1 wt.% La2O3, optimized electrical properties were obtained, which were as follows: epsilon(r) = 1254 (1 kHz), tan gamma = 0.0483, d(33) = 192 pC/N, K-p = 0.27, P-r = 29.1 mu C/cm(2), and E-c = 29.0 kV/cm. (C) 2010 Elsevier B.V. All rights reserved.