Dielectric characteristics and phase structure of lead-free Bi-0.5(Na1-x-yKxAgy)(0.5)TiO3 piezoelectric ceramics

摘要

Lead-free piezoelectric ceramics, Bi-0.5(Na1-x-yKxAgy)(0.5)TiO3, were prepared by a solid-state reaction process, and the dielectric property and phase structure of Bi-0.5(Na1-x-yKxAgy)(0.5)TiO3 ceramics were investigated. XRD patterns show that the MPB of BNKAT(x/0.02) system ceramics lies in the composition range of 0.175 <= x <= 0.20. The relative permittivity epsilon(r) and loss tangent tan delta vary with the K+ content and show a strong temperature- and frequency-dependent behavior in the temperature range measured. The K+ content strongly influences the transition temperature from ferroelectric to anti-ferroelectric phase. In the high-temperature range, the thermal variation of the relative permittivity at various frequencies is well described by the law (1/epsilon(r)) - (1/epsilon(r,m)) =C(T- T-m)(alpha). Such a relaxation behavior may be ascribed to the cations disorder of Na+, K+, Ag+, Bi3+ at A-site. (c) 2007 Elsevier B.V. All rights reserved.