Dielectric and piezoelectric properties of (K_0.5Na_0.5)(Nb_0.97Sb_0.03)O₃ ceramics doped with Bi₂O₃

In this study, to develop the optimal composition of ceramics for low loss piezoelectric actuator and ultrasonic motor applications, (K_0.5Na_0.5)(Nb_0.97Sb_0.03)O₃ + 0.009 K_5.4Cu_1.3Ta₁₀O₂₉ + 0.1wt%Li₂CO₃ + xwt%Bi₂O₃(x = 0 ~ 0.9) lead-free piezoelectric ceramics with a fixed quantity of 0.009 K_5.4Cu_1.3Ta₁₀O₂₉ (abbreviated as KCT) were manufactured using the conventional solid-state solution processes. The effects of Bi₂O₃ addition on the dielectric and piezoelectric properties were then investigated. From the X-ray diffraction analysis result the specimens demonstrated orthorhombic symmetry when Bi₂O₃ was less 0.6 wt%, a pseudo-cubic phase appeared when Bi₂O₃ was 0.9 wt%. SEM images indicate that a small amount of Bi₂O₃ addition affect the microstructure. The piezoelectric properties of (K_0.5Na_0.5)(Nb_0.97Sb_0.03)O₃ ceramics were greatly improved by a certain amount of Bi₂O₃ addition. Excellent properties of density = 4.54 g/cm³, relative densities = 98.5 %, k _p = 0.468, Q _m = 1,715 and d ₃₃ = 183 pC/N were obtained with a composition of 0.3 wt% Bi₂O₃