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Keywords:

  • crystal structure;
  • K0.5Na0.5NbO3;
  • lead-free ceramics;
  • piezoelectric properties

Abstract

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.