Normal sintering and electric properties of (K,Na,Li)(Nb,Sb)O3 lead-free piezoelectric ceramics

Abstract

0.94(K05Na0.5)NbO3−0.03LiNbO3−0.03LiSbO3 (KNLNS) lead-free piezoelectric ceramics were prepared by conventional mixed oxide route with normal sintering method. The samples were sintered at different temperatures with KNLNS powder atmosphere to prevent volatilization of alkali metal oxides at high temperature. The effects of sintering temperature on the density, structure and electric properties of KNLNS ceramics were studied. X-ray diffraction (XRD) results showed that the crystal structure of the crushed KNLNS ceramic powders were pure perovskite phase with tetragonal phase structure when sintered at T ≤ 1080°C. However a K3Li2Nb5O15 phase with tetragonal tungsten bronze structure began to appear when the sintering temperature was higher than 1080°C. The optimum sintering temperature was 1080°C which was determined by measuring the density of the samples. Scanning electron microscope (SEM) observation indicated that the sintering temperature had a great effect on the microstructure of the samples. The KNLNS ceramics under the optimum sintering temperature showed excellent electric properties: ρ = 4.29 g/cm3, e r = 826, tanδ = 0.049, d 33 = 190 pC/N, k p = 0.30, and T c = 385°C. The results show that the KNLNS ceramics are promising candidate for lead-free piezoelectric ceramics.