Effect of poling condition on piezoelectric properties of (K0.5Na0.5)NbO3–LiNbO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics 0.94(K0.5Na0.5)NbO3–0.06LiNbO3 (abbreviated as KNLN6) have been synthesized by traditional ceramics process without cold-isostatic pressing. The phase behavior before poling and after poling was analyzed. The results show that the orthorhombic and tetragonal phase co-exist in KNLN6 ceramics. The effect of poling conditions on piezoelectric properties of KNLN6 ceramics was investigated. The physics mechanism was also discussed. The results show that the optimum poling condition for KNLN6 ceramics is poling electric field of 3.5 kV/mm, poling temperature of 120 °C and poling time of 30 min. Piezoelectric properties of KNLN6 ceramics under the optimum poling condition is piezoelectric constant d33 of 215 pC/N, planar electromechanical coupling factor kp of 0.38, thickness electromechanical coupling factor kt of 0.48, and Curie temperature Tc of 450 °C, respectively. The results show that KNLN6 ceramics is an excellent candidate for lead-free piezoelectric ceramics.