Structure and electrical properties of K0.5Na0.5NbO3–LiSbO3 lead-free piezoelectric ceramics

Abstract

Lead-free piezoelectric ceramics (1−x)K0.5Na0.5NbO3–xLiSbO3 have been fabricated by a conventional ceramic sintering technique. The results of x-ray diffraction suggest that Li+ and Sb5+ diffuse into the K0.5Na0.5NbO3 lattices to form a solid solution with a perovskite structure. The ceramics can be well sintered at 1070–1110°C. The introduction of LiSbO3 into the Na0.5K0.5NbO3 solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature (Tc), but greatly shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition (TO–F) to room temperature. Coexistence of the orthorhombic and tetragonal phases is formed at 0.05<x<0.07 at room temperature, leading to a significant enhancement of the piezoelectric properties. For the ceramic with x=0.06, the piezoelectric properties become optimum: piezoelectric constant d33=212pC∕N, planar and thickness electromechanical coupling factors kP=46% and kt=47%, respectively, remanent polarization Pr=15.0μC∕cm2, coercive field Ec=1.74kV∕mm, and Curie temperature TC=358°C.