Ferroelectric and piezoelectric properties of Bi_(0.5)Na_(0.5)TiO_3-SrTiO_3-Bi_(0.5)Li_(0.5)TiO_3 lead-free ceramics

摘要

New lead-free ternary ceramics (1 -x-y)Bi_(0.5)Na_(0.5)TiO_3-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 deg C. The results of X-ray diffraction reveal that Li~+ and Sr~(2+) diffuse into the Bi_(0.5)Na_(0.5)TiO_3 lattices to form a new solid solution with a single-phase rhombohedral perovskite structure. After the substitutions of Li~+ and Sr~(2+), 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 bccome 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 bccome deformed and the ceramics bccome depolarized.