The microstructure and ferroelectric properties of (K0.5Na0.5)NbO3-LiNbO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (I - x)(K0.5Na0.5)NbO3-xLiNbO(3) have been synthesized by traditional ceramics process without cold-isostatic pressing. Effect of the amount of LiNbO3 on the phase structure, microstructure, ferroelectric and piezoelectric properties of 0 - X)(K0.5Na0.5)NbO3-xLiNbO(3) ceramics were investigated. Results show that the pure perovskite phase is in all ceramics specimens (X < 0.08). With the content of LiNbO3 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 LiNbO3 is 0.06 mol, respectively. However, 0.94(K0.5Na0.5)NbO3-0.06LiNbO(3) ceramics show the optimum piezoelectric properties. The optimum piezoelectric, dielectric and ferroelectric properties for 0.94(K0.5Na0.5)NbO3-0.06LiNbO(3) ceramics are piezoelectric constant d(33) = 215pC/N, planar electromechanical coupling factor k(p) = 0.41, thickness electromechanical coupling factor k(l) = 0.48, Q(m) = 80, P-r = 20.0 mu C/cm(2), E-c = 13.4 kV/cm, relative dielectric constant epsilon(r) = 530, dielectric loss tan delta = 0.034, Curie temperature T-c = 450 degrees C. Compared with other KNN-based piezoelectric ceramics, it can be concluded that 0.94(K0.5Na0.5)NbO3-0.06LiNbO(3) piezoelectric ceramics is a promising candidate for high temperature lead-free piezoelectric ceramics. (c) 2006 Elsevier B.V. All rights reserved.