Relaxor nature in Ba 5 RZr 3 Nb 7 O 30 (R = La, Nd, Sm) tetragonal tungsten bronze new system

Ba 5 RZ r 3 Nb 7 O 30 (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 P 4 /mbm was determined for all compositions, ion cross distribution by Ba 2+ and R 3+ in A 1 site was observed, while A 2 site was only occupied by Ba 2+ . 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 A 1 site ion size. Slim P‐E hysteresis loops were obtained at room temperature for all compositions. Meanwhile, micro ferroelectric domains were observed in Ba 5 SmZr 3 Nb 7 O 30 . For Ba 4 R 2 Zr 4 Nb 6 O 30 and Ba 5 RZ r 3 Nb 7 O 30 (R = Nd, Sm), the transition from normal ferroelectric to relaxor behavior originates from the increased t A 1 , which is a result of cross distribution at A 1 site. Compared with Ba 5 RT i 3 Nb 7 O 30 , Zr substitution at B site enhances the relaxor nature.