The microstructure and ferroelectric 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. Effect of the amount of LiNbO 3 on the phase structure, microstructure, ferroelectric and piezoelectric properties of (1 − x)(K 0.5Na 0.5)NbO 3– xLiNbO 3 ceramics were investigated. Results show that the pure perovskite phase is in all ceramics specimens ( x < 0.08). With the content of LiNbO 3 increases, remnant polarization P r, coercive field E c and mechanical quality factor Q m decrease. P r and E c show their minimum in this system when the amount of LiNbO 3 is 0.06 mol, respectively. However, 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3 ceramics show the optimum piezoelectric properties. The optimum piezoelectric, dielectric and ferroelectric properties for 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3 ceramics are piezoelectric constant d 33 = 215pC/N, planar electromechanical coupling factor k p = 0.41, thickness electromechanical coupling factor k t = 0.48, Q m = 80, P r = 20.0 μC/cm 2, E c = 13.4 kV/cm, relative dielectric constant ɛ r = 530, dielectric loss tan δ = 0.034, Curie temperature T c = 450 °C. Compared with other KNN-based piezoelectric ceramics, it can be concluded that 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3 piezoelectric ceramics is a promising candidate for high temperature lead-free piezoelectric ceramics.