In this paper, piezoelectric ceramics with the composition of (Na0.525K0.4425Li0.0375)(Nb0.8975Sb0.065Ta0.0375)O3 + 0.3 wt% CoO + x CuO (0.005≤x≤0.025) (abbreviated to NKL-NST) were fabricated for ultrasonic sensor application. The effects of CuO addition and sintering on the microstructure and the piezoelectric properties of the NKL-NST ceramics were systematically studied. Excellent piezoelectric properties such as electromchanical coupling factor(kp) = 0.415, piezoelectric constant (d33) =166 pC/N and piezoelectric figure of merit d33*g33= 5.47 pm2/N were obtained from the 2.5 mol% CuO doped NKL-NST+0.3 wt%CoO ceramics sintered at 1,000℃ for 3 h.
