Structure, microstructure, and piezoelectric properties of ytterbium-doped potassium sodium niobate lead-free ceramics

The structure, microstructure, and piezoelectric properties of conventionally sintered Yb-doped K_0.5Na_0.5NbO₃ (KNN) lead-free ceramics were investigated. Doping the KNN ceramics with Yb₂O₃ was effective in inhibiting the grain growth in the KNN ceramics and in densifying the ceramics. The 1.0 wt. % Yb-doped KNN ceramics showed the maximum density, about 96.8% of the theoretical density. X-ray diffraction analysis showed that a small number of Yb³⁺ ions could be incorporated into the matrix of the ceramicsto occupythe α- or β-sites in the crystal lattice, thereby significantly affecting the piezoelectric properties of the ceramics. Enhanced piezoelectric properties (i.e., d ₃₃= 135 pC/N, k _p = 34.5%, and Q _m = 80.2) were obtained for the 0.50 wt. % Yb-doped KNN ceramics.