Ferroelectric and piezoelectric properties of [(Bi_0.98La_0.02Na_1-xLi_x)_0.5]_0.94Ba_0.06TiO₃lead-free ceramics

Lead-free ceramics [(Bi0.98La0.02Na1-xLix)0.5]0.94Ba0.06TiO3have been prepared by an ordinary sintering technique and their ferroelectric and piezoelectric properties have been studied. The results of X-ray diffraction reveal that Li+, Ba2+, and La3+diffuse into the Bi0.5Na0.5TiO3lattices to form a new solid solution with a pure perovskite structure. The partial substitution of Li+lowers the coercive field Ecand improves the remanent polarization Pr. Because of the larger Prand lower Ec, the ceramic with x = 0.10 exhibits optimum piezoelectric properties: d33= 212 pC/N and kP= 36.1%. The partial substitution of Li+for Na+shifts the depolarization temperature Tdtoward low temperature. The ceramics exhibit relaxor characteristic, which is probably resulted from the cation disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties suggest that the ceramics contain both the polar and non-polar regions near/above Td, which cause the polarization hysteresis loop become deformed and the ceramics become depolarized.