Phase structures and electrical properties of K0.5Na0.5(Nb0.925Ta0.075)O3–LiSbO3lead-free piezoelectric ceramics

Lead-free ceramics (1- x )K 0.5 Na 0.5 (Nb 0.925 Ta 0.075 )O 3 - x LiSbO 3 have been prepared by an ordinary sintering technique. Our results reveal that Li + and Sb 5+ diffuse into the K 0.5 Na 0.5 (Nb 0.925 Ta 0.075 )O 3 lattices to form a solid solution with a perovskite structure. The introduction of LiSbO 3 into K 0.5 Na 0.5 (Nb 0.925 Ta 0.075 )O 3 decreases the Curie temperature ( T c ) slightly, but shifts the ferroelectric tetragonal–ferroelectric orthorhombic phase transition temperature ( T O−T ) significantly to low temperatures. As a result, the ceramics have an orthorhombic phase at x ≤ 0.02 and tetragonal phase at x ≥ 0.04. Coexistence of the orthorhombic and tetragonal phases is formed at 0.02 < x < 0.04 near room temperature, leading to significant enhancements of the piezoelectric properties. For the ceramic with x = 0.035, the piezoelectric properties become optimum giving: piezoelectric coefficient d 33 = 244 pC N −1 , electromechanical coupling factors k P = 51% and k t = 46%, remanent polarization P r = 20.1 µC cm −2 , coercive field E c = 1.37 kV mm −1 and Curie temperature T c = 354 °C. The ceramic has good temporal and thermal stability, greatly improved electrical properties and a relatively high Curie temperature, suggesting that it is a promising lead-free replacement for lead-based piezoelectric ceramics.