Piezoelectric and ferroelectric properties of KxNa1−xNbO3 lead-free ceramics with MnO2 and CuO doping

Lead-free ceramics KxNa1−xNbO3 doped with MnO2 and CuO have been fabricated by an ordinary ceramic technique. The ceramics have an orthorhombic perovskite structure. Our results indicate that the doping of MnO2 and CuO is effective in promoting the densification of the ceramics. The MnO2-doped KxNa1−xNbO3 ceramics retain the strong ferroelectricity, with the remanent polarization Pr and coercive field Ec decrease slightly with the amount of MnO2. The ceramics also possess a high piezoelectric coefficient (d33 = 105–108 pC/N) and relatively large electromechanical coupling factors (kp = 0.43–0.47 and kt = 0.46–0.48). The KxNa1−xNbO3 ceramics co-doped with MnO2 and CuO exhibit a high mechanical quality factor (Qm ∼ 1205) as well as relatively large kp and kt, suggesting that the ceramics are the promising candidates for the transducer and transformer applications.