Structural and Physical Properties of Mixed-Layer Aurivillius-Type Multiferroics

Different from the homogeneous layer structure of famous Bin+1Fen−3Ti3O3n+3 compounds with integer n values, the mixed‐layer structure of the compounds with fractional n values and their related physics have been rarely reported in recent years. In this work, the mixed‐layer compound Bi11Fe3Ti6O33 (n = 4.5) was synthesized by the modified Pechini method, and its structure was characterized as an inhomogeneous phase generating from the disordered intergrowths of the n = 4 and 5 perovskite slabs. Multiferroic properties of this compound were discussed in detail, compared with two adjacent homologous Aurivillius phases Bi5FeTi3O15 (n = 4) and Bi6Fe2Ti3O18 (n = 5). Significantly, the ferroelectric polarization of the mixed‐layer sample at room temperature is higher than that of the adjacent homologous phases with integer n, mainly arising from the intrinsic mixed‐layer structure. The ferroelectric Curie temperature (~992 K) and a magnetic transition temperature (~7 K) of the 4.5‐layer phase of Bi11Fe3Ti6O33 fall in between those of the homogeneous 4‐ and 5‐layer phases, conforming to the change trends of such oxides with integer n. These results provide important contributions to understand the Aurivillius‐type materials and open up a new avenue to enhance multiferroic properties in single‐phase multiferroics.