Wide phase boundary zone, piezoelectric properties, and stability in 0.97(K_0.4Na_0.6)(Nb_1-xSb_x)O ₃-0.03Bi_0.5Li_0.5ZrO₃ lead-free ceramics

In this work, the rhombohedral (R) and tetragonal (T) phase boundary of the 0.97(K_0.4Na_0.6)(Nb_1-xSb_x)O ₃-0.03Bi_0.5Li_0.5ZrO₃ piezoceramics has been attained in a wide composition range of 0.035 ≤ x ≤ 0.08, and the Sb⁵⁺ could simultaneously shrink its T_R-O and T _O-T. A giant d₃₃ of 380-405 pC N^-1 and a T _C of 200-292 °C have been observed in the ceramics with the coexistence of both R and T phases. In addition, the ceramics with 0.035 ≤ x ≤ 0.08 also show a good thermal stability of the d₃₃, and an enhanced temperature stability of ferroelectricity could be observed in the ceramic with x = 0.035. As a result, adding the optimum antimony content is an efficient way to promote the electrical properties of potassium-sodium niobate ceramics with the R-T phase boundary.