Ferroelectric and piezoelectric properties of Bi0.5Na0.5TiO3-SrTiO3-Bi0.5Li0.5TiO3 lead-free ceramics

New lead-free ternary ceramics (1 - x - y)Bi0.5Na0.5TiO3-xSrTiO(3)-yBi(0.5)Li(0.5)TiO(3) have been prepared by an ordinary sintering technique and their ferroelectric and piezoelectric properties have been studied. All the ceramics can be well-sintered at 1100 degrees C. The results of X-ray diffraction reveal that Li+ and Sr2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a single-phase rhombohedral perovskite structure. After the substitutions of Li+ and Sr2+, the coercive field E-C decreases, the remanent polarization P-r increases, and hence the piezoelectric coefficient d(33) and planar electromechanical coupling factor k(P) increase. For the ceramics with x = 0.13-0.15 and y = 0.10-0.15, the piezoelectric properties become optimum, giving d(33) = 127-146 pC/N and k(P) = 0.24-0.30. Our results also suggest that the ceramics may contain both the polar and non-polar regions near the depolarization temperature T-d, which cause the polarization hysteresis loop become deformed and the ceramics become depolarized. (C) 2009 Elsevier B.V. All rights reserved.