Effects of Sb content on electrical properties of lead-free piezoelectric [(Na0.535K0.480)0.942Li0.058](Nb1−xSbx)O3 ceramics

Lead-free piezoelectric [(Na0.535K0.480)0.942Li0.058](Nb1−xSbx)O3 (x = 2–8 mol%) ceramics were fabricated by normal sintering at 1040 °C for 2 h. The phase structure, microstructure and electrical properties were investigated with a special emphasis on the influence of the Sb content. All samples exhibit a single perovskite structure with an orthorhombic symmetry over the whole compositional range, whereby the [(Na0.535K0.480)0.942Li0.058](Nb0.94Sb0.06)O3 ceramic shows the peak values of the piezoelectric coefficient (d33), electromechanical coupling coefficient (kp), and dielectric constant (ɛ), which are 298 pC/N, 34.5% and 945, respectively, owing to the biggest grain size and the densest microstructure. Transitional point from orthorhombic to tetragonal phase (TO–T) appears in the range of 60–70 °C and shows a decreased trend with increasing Sb content. Two cubic points (TT–C) from the tetragonal phase to the cubic phase were found, which might be caused by the possibility of Sb-rich and Sb-lacked areas existed in the ceramics.