Effects of Bi substitution on the structures, electrical properties, and transparency of Sr2Na1−3Bi Nb5O15 ceramics

Abstract Sr2Na1−3xBixNb5O15 ceramics (SNBN; x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08) were synthesized by a conventional solid-state reaction method. To eliminate the impurity phase in the Sr2NaNb5O15 ceramics, we introduced high-charge Bi3+ into the SNN ceramics to reduce the filling degree of A1 and A2 sites. X-ray diffraction results confirmed this compositional design, because all SNBN ceramics showed a pure tetragonal tungsten-bronze phase along with shrinkage of the unit cell when x > 0.01. Meanwhile, Bi3+ introduction improved their dielectric , ferroelectric , and transparent properties. As suggested by Raman and SEM, both the higher densification with relatively uniform grain size and more distorting degree of the NbO 6 polar unit contributed to the enhanced electrical properties and transparency at x = 0.04.