Dielectric and piezoelectric properties of K₀.₅ Na₀.₅ NbO₃-AgSbO₃lead-free ceramics

Abstract

Lead-free piezoelectric ceramics (1−x) K₀.₅Na₀.₅NbO₃–xAgSbO₃+0.75 mol % MnO₂were prepared by a conventional solid-state sintering technique, and the piezoelectric and dielectric properties of the ceramics were studied. The results of x-ray diffraction suggest that AgSbO₃diffuses into the K₀.₅Na₀.₅NbO₃lattices to form a new solid solution with a single-phase orthorhombic perovskite structure. After the addition of AgSbO₃, the paraelectric cubic-ferroelectric tetragonal phase transition temperature (Tc) and the ferroelectric tetragonal-ferroelectric orthorhombic phase transition temperature (T[sub O-T]) decrease, and the ceramics become “softened,” resulting in significant improvements in the ferroelectric and piezoelectric properties. The ceramics with x=0.03–0.10 exhibit excellent piezoelectric properties: D₃ ₃=130–216 pC/N, k[sub p]=0.44–0.51, and k[sub t]=0.40–0.52. The ceramics also exhibit a good thermal stability up to high T[sub O-T], suggesting that the ceramics are promising candidates for lead-free piezoelectric ceramics.