Influence of sintering temperature on piezoelectric properties of (K0.5Na0.5)NbO3–LiNbO3 lead-free piezoelectric ceramics

Abstract Lead-free piezoelectric ceramics (1 − x )(K 0.5 Na 0.5 )NbO 3 – x LiNbO 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 0.5 Na 0.5 )NbO 3 – x LiNbO 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 0.5 Na 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 0.5 Na 0.5 )NbO 3 – x LiNbO 3 decreases with the increase of the content of LiNbO 3 . The optimum composition for (1 − x )(K 0.5 Na 0.5 )NbO 3 – x LiNbO 3 ceramics is 0.94(K 0.5 Na 0.5 )NbO 3 –0.06LiNbO 3 . The optimum sintering temperature of 0.94(K 0.5 Na 0.5 )NbO 3 –0.06LiNbO 3 ceramics is 1080 °C. Piezoelectric properties of 0.94 (K 0.5 Na 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 0.5 Na 0.5 )NbO 3 –0.06LiNbO 3 piezoelectric ceramics is a promising candidate for lead-free piezoelectric ceramics.