Piezoelectric Properties and Depolarization Temperature of NaNbO3-LiNbO3 Lead-Free Piezoelectric Ceramics

Piezoelectric and dielectric properties of (LixNa1-x)NbO3 (LNN100x; x≤0.14) ceramics were investigated according to phase transition The highest electromechanical coupling factor, kp, of 0.247 was obtained for LNN12 which has a composition with a morphotropic phase boundary at room temperature. On the other hand, the coupling factor of k33 with longitudinal mode was almost constant for all compositions of x. The dielectric constant, ε r, before poling treatment exhibited a thermal hysteresis near the Curie temperature, TC, for all compositions. The depolarization temperature of LNN6 was higher than the TC before poling treatment. In addition, the peak of free permittivity, ε33 T, was shifted to higher temperature. It was considered that the phase transition was induced by the electric field during poling treatment.