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

Different from the homogeneous layer structure of famous Bi n +1 Fe n −3 Ti 3 O 3 n +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 Bi 11 Fe 3 Ti 6 O 33 ( 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 Bi 5 FeTi 3 O 15 ( n = 4) and Bi 6 Fe 2 Ti 3 O 18 ( 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 Bi 11 Fe 3 Ti 6 O 33 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.