Phase structure, dielectric, and piezoelectric properties of (K_(0.94-x)Na_xLi_(0.06))(Nb_(0.94)Sb_(0.06))O_3 lead-free ceramics

摘要

Lead-free piezoelectric ceramics (K_(0.94-x)Na_xLi_(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 ℃ with x increasing from 0.35 to 0.55 and then increases from 84 to 144 ℃ with x further increasing from 0.6 to 0.7, while the Curie temperature T_c deceases from 388 to 348 ℃ 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.