Dielectric and piezoelectric properties of K_0.5Na_0.5NbO₃- AgSbO₃lead-free ceramics

Lead-free piezoelectric ceramics (1-x) K0.5Na0.5NbO3-x AgSbO3+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 (TO-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: d33=130-216 pC/N, kp=0.44-0.51, and kt=0.40-0.52. The ceramics also exhibit a good thermal stability up to high TO-T, suggesting that the ceramics are promising candidates for lead-free piezoelectric ceramics.