Structure, electrical properties and depolarization temperature of (Bi0.5Na0.5)TiO3–BaTiO3 lead-free piezoelectric ceramics

Lead-free ceramics (1 − x)Bi0.5Na0.5TiO3–xBaTiO3 have been prepared by a conventional solid reaction method, and their structure, electrical properties and depolarization temperature have been studied. The results of X-ray diffraction reveal that Ba2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at 0.06 < x < 0.10. The grain size decreases with x. After the introduction of BaTiO3 into Bi0.5Na0.5TiO3, the ceramics exhibit a lower coercive field Ec and a larger remanent polarization Pr. Because of the strong ferroelectricity and MPB, the ceramics with x = 0.06 exhibit optimum piezoelectric properties: d33 = 155 pC/N and kP = 36.7%. The depolarization temperature Td shows a strong compositional dependence and gives a minimum value at MPB. In addition, the ceramics exhibit relaxor characteristic, which probably results from the cation disordering in the 12-fold coordination sites. The results of the ferroelectric and dielectric properties at high temperatures may suggest that the ceramics may contain both the polar and non-polar regions at temperatures above Td.