Phase structure, dielectric, and piezoelectric properties of (K_0.94−xNa_xLi_0.06)(Nb_0.94Sb_0.06)O₃ lead‐free ceramics

Abstract Lead‐free piezoelectric ceramics (K_0.94−xNa_xLi_0.06)(Nb_0.94Sb_0.06)O₃ have been fabricated by a conventional ceramic technique and the effects of K⁺/Na⁺ ratio on the structure and piezoelectric properties of the ceramics have been studied. All the ceramics possess a pure perovskite structure. The coexistence of tetragonal and orthorhombic phases is formed at room temperature in the ceramics with 0.45 ≤ x ≤ 0.55. The tetragonal–orthorhombic phase‐transition temperature T_O–T decreases from 110 to 54 °C with x increasing from 0.35 to 0.55 and then increases from 84 to 144 °C with x further increasing from 0.6 to 0.7, while the Curie temperature T_C deceases from 388 to 348 °C with x increasing from 0.35 to 0.70. Because of the coexistence of the two phases near room temperature, the ceramics with x = 0.50 exhibit the optimum piezoelectric properties: d₃₃ = 230 pC/N and k_p = 49%. The ceramics possess good time stability of piezoelectric properties.