Lead-free Na0.5K0.5NbO3 piezoelectric ceramics fabricated by spark plasma sintering: Annealing effect on electrical properties

Niobate ceramics such as NaNbO3 and KNbO3 have been studied as promising Pb-free piezoelectric ceramics, but their sintering densification is fairly difficult. In the present study, highly dense Na0.5K0.5NbO3 ceramics with submicron grains were prepared using SPS, whose density was raised to 4.47 g/cm3 (>99% of the theoretical density) at 920 °C. Reasonably good ferroelectric and piezoelectric properties were obtained in the SPSed Na0.5K0.5NbO3 ceramics after annealing in air. The effect of annealing time on the electrical properties was investigated to determine optimal processing condition. The piezoelectric parameter (d33) of the Na0.5K0.5NbO3 ceramics annealed properly reached 148 pC/N.