Influence of sintering temperature on piezoelectric properties of (K 0.5Na 0.5)NbO 3–LiNbO 3 lead-free piezoelectric ceramics

Abstract

Lead-free piezoelectric ceramics (1 − x)(K 0.5Na 0.5)NbO 3– xLiNbO 3 have been synthesized by traditional ceramics process without cold-isostatic pressing. The effect of the content of LiNbO 3 and the sintering temperature on the phase structure, the microstructure and piezoelectric properties of (1 − x)(K 0.5Na 0.5)NbO 3– xLiNbO 3 ceramics were investigated. The result shows that the phase structure transforms from the orthorhombic phase to tetragonal phase with the increase of the content of LiNbO 3, and the orthorhombic and tetragonal phase co-exist in (K 0.5Na 0.5)NbO 3–LiNbO 3 ceramics when the content of LiNbO 3 is about 0.06 mol. The sintering temperature of (1 − x)(K 0.5Na 0.5)NbO 3– xLiNbO 3 decreases with the increase of the content of LiNbO 3. The optimum composition for (1 − x)(K 0.5Na 0.5)NbO 3– xLiNbO 3 ceramics is 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3. The optimum sintering temperature of 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3 ceramics is 1080 °C. Piezoelectric properties of 0.94 (K 0.5Na 0.5)NbO 3–0.06LiNbO 3 ceramics under the optimum sintering temperature are piezoelectric constant d 33 of 215 pC/N, planar electromechanical coupling factor k p of 0.41, thickness electromechanical coupling factor k t of 0.48, the mechanical quality factor Q m of 80, the dielectric constant of 530 and the Curie temperature T c = 450 °C, respectively. The results indicate that 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3 piezoelectric ceramics is a promising candidate for lead-free piezoelectric ceramics.