Improving the piezoelectric strain and anti-reduction properties of K0.5Na0.5NbO3-based ceramics sintered in a reducing atmosphere.

Lead-free 0.945K0.48Na0.52Nb0.96Ta0.04O3-0.055BaZrO3 + 6%MnO + xZrO2 piezoelectric ceramics sintered in a reducing atmosphere were prepared by conventional solid-state reaction methods. The use of the ZrO2 dopant resulted in an increase in the rhombohedral (R) phase in orthorhombic (O)/R coexisting phases. Nonstoichiometric ZrO2 dopant addition could effectively improve the anti-reduction properties of KNN-based ceramics via controlling the oxygen vacancy concentration. In particular, 2% mol nonstoichometric ZrO2 dopant addition could improve the activation energy of the grain boundary (Egb) via increasing the grain boundary thickness. The addition of the ZrO2 dopant could improve the fatigue resistance of the unipolar piezoelectric strain of 0.945K0.48Na0.52Nb0.96Ta0.04O3-0.055BaZrO3 + 6%MnO ceramics. The optimum inverse piezoelectric coefficient of ceramics at x = 0.01 reached up to ∼465 pm V-1 at a low driving electric field E of 20 kV cm-1 at room temperature, and the temperature stability of reached 155 °C. After 106 unipolar fatigue cycles, the ß value of 0.945KNNT-0.055BZ + 6Mn + xZr ceramics could be preserved to more than 86%. The 0.945K0.48Na0.52Nb0.96Ta0.04O3-0.055BaZrO3 + 6%MnO + xZrO2 ceramic is a lead-free material with great potential to be applied in the fabrication of multilayer ceramic actuators with Ni inner electrodes in the future.