Piezoelectric and dielectric properties of (Na_0.5K_0.5)NbO₃-Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ lead-free ceramics

Abstract

Lead-free piezoelectric ceramics (1-x)(Na_0.5K_0.5)NbO₃-xBi_0.5(Na_0.8K_0.2)_0.5TiO₃ (abbreviated as NKN-BNKT100x, with x ranges from 0 to 0.08 mol) have been synthesized by a conventional solid state sintering method. The effects of amount of BNKT-content on electrical properties and crystalline structures have been investigated. X-ray diffraction analysis showed that a morphotropic phase boundaries (MPB) between orthorhombic and tetragonal phases exists in the composition range of 0.05 < x < 0.06, near which the dielectric and piezoelectric properties are enhanced. The NKN-BNKT5 ceramics exhibits good properties (d₃₃ = 216pC/N, k_p = 41%, ε₃₃^T/ε₀ = 1315). These results indicate that NKN-BNKT100x ceramic is a promising lead-free piezoelectric candidate material.