Ferroelectric and piezoelectric properties of [(Bi0.98La0.02Na1−x Li x )0.5]0.94Ba0.06TiO3 lead-free ceramics

Lead-free ceramics [(Bi0.98La0.02Na1−x Li x )0.5]0.94Ba0.06TiO3 have 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 Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure. The partial substitution of Li+ lowers the coercive field E c and improves the remanent polarization P r. Because of the larger P r and lower E c, the ceramic with x = 0.10 exhibits optimum piezoelectric properties: d 33 = 212 pC/N and k P = 36.1%. The partial substitution of Li+ for Na+ shifts the depolarization temperature T d toward 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 T d, which cause the polarization hysteresis loop become deformed and the ceramics become depolarized.