Phase structure, dielectric, and piezoelectric properties of (K0.94-xNaxLi0.06)(Nb0.94Sb0.06)O3 lead-free ceramics

Lead-free piezoelectric ceramics (K0.94-xNaxLi0.06)(Nb0.94Sb0.06)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 TO-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 TC 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 kp = 49%. The ceramics possess good time stability of piezoelectric properties. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)