Effect of Li-substitution on piezoelectric and ferroelectric properties of (Bi0.92Na0.92−xLix)0.5Ba0.06Sr0.02TiO3 lead-free ceramics

New lead-free ceramics (Bi0.92Na0.92−xLix)0.5Ba0.06Sr0.02TiO3 have been fabricated by a conventional ceramic technique and their electrical properties have been studied. X-ray diffraction studies reveal that Li+, Ba2+ and Sr2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure. The partial substitution of Li+ for Na+ increases the remanent polarization Pr of the ceramics. Because of the large Pr and low coercive field Ec, the ceramics with x = 0.075–0.125 exhibit excellent piezoelectric properties: d33 = 189–235 pC/N, kp = 33.6–36.3% and kt = 51.6–54.3%. The ceramics exhibit relaxor behaviors after the substitution of Li+ for Na+. Our results also suggest that polar and non-polar phases may coexist in the ceramics at temperatures above the depolarization temperature Td.