Relaxor nature in Ba5RZr3Nb7O30 (R = La,Nd, Sm) tetragonal tungsten bronze new system

Ba₅RZr₃Nb₇O₃₀(R = La, Nd, Sm) lead‐free relaxor ferroelectrics were prepared by a standard solid‐state reaction process, and the influence of A and B site ion occupation on the dielectric characteristics especially the relaxor nature were investigated systematically. Tetragonal tungsten bronze structure with space group P4/mbm was determined for all compositions, ion cross distribution by Ba²⁺ and R³⁺ in A1 site was observed, while A2 site was only occupied by Ba²⁺. Selected area electron diffraction patterns confirmed the existence of incommensurate superlattice modulation. Furthermore, temperature and frequency dependences of the dielectric properties showed a broad permittivity peak with strong frequency dispersion, following well the Vogel‐Fulcher relationship. The maximum dielectric constant temperature increased gradually with decreasing A1 site ion size. Slim P‐E hysteresis loops were obtained at room temperature for all compositions. Meanwhile, micro ferroelectric domains were observed in Ba₅SmZr₃Nb₇O₃₀. For Ba₄R₂Zr₄Nb₆O₃₀ and Ba₅RZr₃Nb₇O₃₀ (R = Nd, Sm), the transition from normal ferroelectric to relaxor behavior originates from the increased t_A1, which is a result of cross distribution at A1 site. Compared with Ba₅RTi₃Nb₇O₃₀, Zr substitution at B site enhances the relaxor nature.