Phase structure, dielectric, and piezoelectric properties of (K 0.94− x Na x Li 0.06 )(Nb 0.94 Sb 0.06 )O 3 lead‐free ceramics

Lead‐free piezoelectric ceramics (K 0.94− x Na x Li 0.06 )(Nb 0.94 Sb 0.06 )O 3 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: d 33  = 230 pC/N and k p  = 49%. The ceramics possess good time stability of piezoelectric properties.