Physical and Electrical Properties of Lead-Free (Bi_0.5Na_0.5)TiO₃-(Na_0.5K_0.5)NbO₃ Ceramics

Abstract

Lead-free (1-x)(Bi0.5Na0.5)TiO3–x(Na0.5K0.5)NbO3(x<0.1) ceramics have been prepared by the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the (Na0.5K0.5)NbO3diffuse into the lattice of (Bi0.5Na0.5)TiO3to form a solid solution and the hexagonal phase with a perovskite structure. The samples with a low content of (Na0.5K0.5) NbO3exhibit relatively good physical and electrical properties. For 0.96(Bi0.5Na0.5) TiO3–0.04 (Na0.5K0.5) NbO3ceramics, the electromechanical coupling coefficients of the planar modekpand the thickness modektreach 0.25 and 0.52, respectively, after sintering at 1100 °C for 5 h. The ratio of the thickness coupling coefficient to the planar coupling coefficient is 2.08. With suitable (Na0.5K0.5)NbO3concentration and sintering conditions, a dense microstructure and good electrical properties are obtained. Our results show that 0.96(Bi0.5Na0.5)TiO3–0.04(Na0.5K0.5)NbO3solid solution ceramics are promising lead-free ceramics for high-frequency electromechanical transducer applications.