Properties of (Na0.53K0.4Li0.07)Nb1-x%Sbx%O3 ceramics with high lithium and antimony content

(Na0.53K0.4Li0.07)Nb1-x%Sbx%O3 (NKLNSx) piezoelectric ceramics with high content of lithium and antimony have been prepared by the solid-state reaction technique. The effect of Sb content on the crystallographic structure, phase transitions, piezoelectric and ferroelectric properties of NKLNSx ceramics is studied. The X-ray diffraction results suggest that the structure of the ceramics changes from pure tetragonal phase to the coexistence of orthorhombic and tetragonal phases with the increasing x, and that a little amount of second phase, LiSbO3, is formed. The increase of Sb content induces a decrease of the Curie temperature TC and an increase of the orthorhombic-tetragonal phase transition temperature TO-T. The two compositions, NKLNS8.8 and NKLNS9.1, with TO-T closest to room temperature, possess optimum properties, with d33 ∼ 290 pC/N, εr ∼ 1340, and Pr ∼ 24.2 μC/cm2. These properties are superior to those of previously reported (K, Na, Li)(Nb, Sb)O3 systems with low content of lithium and antimony. The thermal stability investigations show that the change of kp is minor for the ceramics that do not undergo a phase transition in the examined temperature range.