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 anorthorhombic 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 P-r and coercive field E-c decrease slightly with the amount of MnO2. The ceramics also possess a high piezoelectric coefficient (d(33) = 105-108 pC/N) and relatively large electromechanical coupling factors (k(p) = 0.43-0.47 and k(t) = 0.46-0.48). The KxNa1-xNbO3 ceramics co-doped with MnO2 and CuO exhibit a high mechanical quality factor (Q(m) similar to 1205) as well as relatively large k(p) and k(t), suggesting that the ceramics are the promising candidates for the transducer and transformer applications. (C) 2007 Elsevier B.V. All rights reserved.