Sb doping effects on the piezoelectric and ferroelectric characteristics of lead-free Na_0.5K_0.5Nb_1-x Sb_xO ₃ piezoelectric ceramics

The piezoelectric, phase structure and ferroelectric properties of lead-free Na_0.5K_0.5Nb_1-xSb_xO ₃ piezoelectric ceramics were systematically investigated. (Na _0.5K_0.5)Nb_1-xSb_xO₃ ceramics were synthesized using the conventional solid-state reaction method. The effect of B-site Sb⁵⁺ substitution for Nb⁵⁺ on the structural characteristics and piezoelectric properties of samples was determined. According to XRD patterns, the phase gradually changes from tetragonal to orthorhombic with increasing Sb content. At x = 0.03, the tetragonal and orthorhombic phases coexist and relatively high piezoelectric properties were obtained. The relatively high Q_m value obtained after substitution with Sb⁵⁺ ions might be due to the increased electronegativity and decreased ionic radius at the morphotropic phase boundary (MPB) at x = 0.03. However, the Q_m value decreases with further Sb addition. Relatively high piezoelectric properties at x = 0.03 of k_p = 0.42, k_t = 0.48, ε_r = 446, Q_m = 143, tan δ = 2.3%, and density = 4.31 g/cm³, d₃₃ = 123 pC/N, were obtained.