Structure and electrical properties of Bi0.5Na0.5TiO3-Y0.5Na0.5TiO3-BaTiO3 lead-free piezoelectric ceramics

New (1 – x − y)Bi0.5Na0.5TiO3-xY0.5Na0.5TiO3-yBaTiO3 lead-free ceramics have been prepared by a conventional ceramic fabrication technique, and their structure and electrical properties have been studied. A morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases is formed at 0.04 < y < 0.10. As compared to pure Bi0.5Na0.5TiO3 ceramic, the partial substitutions of Y3+ for Bi3+ and Ba2+ for (Bi0.5Na0.5)2+ in the A-sites of Bi0.5Na0.5TiO3 lower effectively the coercive field Ec and increase the remanent polarization Pr of the ceramics. Because of low Ec, large Pr and the MPB, the ceramics with x = 0–0.02 and y = 0.06 exhibit the optimum piezoelectric properties: d33 = 155–159 pC/N and kp = 28.8–36.7%. The temperature dependences of dielectric properties of the ceramics show relaxor-like behaviors. The ferroelectric properties at different temperature suggest that the ceramics may contain both the polar and non-polar regions near/above Td.