Sintering characteristic, microstructure, and dielectric relaxor behavior of (K_0.5Na_0.5)NbO₃-(Bi_0.5Na _0.5)TiO₃ lead-free ceramics

Highly dense lead-free ceramics (1-x)(K_0.5Na_0.5) NbO₃-x(Bi_0.5Na_0.5)TiO₃ [(1-x)KNN-xBNT] have been synthesized by pressureless sintering owing to the careful control of processing conditions. The densification of (1-x)KNN-xBNT ceramics improves with increasing addition of BNT. The translucence is observed in 0.96 KNN-0.04 BNT ceramics. Diffuse phase transition and frequency dispersion of the dielectric constant, which are two typical characteristics for relaxor ferroelectrics, are observed in (1-x)KNN-xBNT ceramics. Dielectric relaxor behavior obeys a modified Curie-Weiss law. In addition, (1-x)KNN-xBNT ceramics possess a high Curie temperature (>320°C). The results indicate that (1-x)KNN-xBNT (x=0.06) ceramics are promising lead-free candidate relaxor ferroelectrics for high-temperature applications.