Piezoelectric properties of low-temperature sintered Li-modified (Na, K)NbO_3 lead-free ceramics

摘要

LiNbO_3-doped (Na, K)NbO_3 lead-free piezoceramics were prepared by conventional sintering at a temperature as low as 950℃ using excess Na_2O additives. The crystal structure changed from orthorhombic to tetragonal with increasing LiNbO_3 amount since the phase transition temperature T_(O-T) shifted downward. In the region of two-phase coexistence, enhanced piezoelectric constant d_(33) (280 pC/N) and electromechanical coupling factor k_p (48.3%) with a high Curie temperature T_C (475℃) were obtained in the nominal composition 0.92(Na_(0.535)K_(0.48))NbO_3-0.08LiNbO_3. Our results open up the way to low-temperature sintering of (Na, K)NbO_3-based lead-free piezoceramics with high performance.