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

Lead-free piezoelectric ceramics (1-x)K0.5Na0.5NbO3-xLiSbO(3) 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 degrees C. The introduction of LiSbO3 into the Na0.5K0.5NbO3 solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature (T-c), 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 d(33)=212 pC/N, planar and thickness electromechanical coupling factors k(P)=46% and k(t)=47%, respectively, remanent polarization P-r=15.0 mu C/cm(2), coercive field E-c=1.74 kV/mm, and Curie temperature T-C=358 degrees C. (c) 2007 American Institute of Physics.