Sb doping effects on the piezoelectric and ferroelectric characteristics of lead-free Na0.5K0.5Nb1−x SbxO3 piezoelectric ceramics

The piezoelectric, phase structure and ferroelectric properties of lead-free Na0.5K0.5Nb1−xSbxO3 piezoelectric ceramics were systematically investigated. (Na0.5K0.5)Nb1−xSbxO3 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 Qm 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 Qm value decreases with further Sb addition. Relatively high piezoelectric properties at x = 0.03 of kp = 0.42, kt = 0.48, ɛr = 446, Qm = 143, tan δ = 2.3%, and density = 4.31 g/cm3, d33 = 123 pC/N, were obtained.