A Large Family of Iron Ruddlesden‐Popper Relatives: from Oxides to Oxycarbonates and Oxyhydroxides

Iron oxides, oxyhydroxydes and oxycarbonates derived from the layered Ruddlesden‐Popper (RP) structure form a large family of layered compounds. Besides the classical RP oxides Srn+1FenO3n+1, single intergrowths with the generic formulation (A,Sr)n+2FenO3n+2 and (A,Sr)n+3FenO3n+3 (A = Tl, Pb, Bi…) can be generated by increasing the multiplicity of the rock salt layers, and multiple intergrowths of these single intergrowths can be synthesized. Starting from oxygen deficient RP oxides such as n = 3 member Sr3NdFe3O9−δ, oxyhydroxydes hydrates and oxyhydroxydes such as Sr3NdFe3O7.5(OH)2·H2O and Sr3NdFe3O7.5(OH)2 can be created topotactically. Carbonate groups can also replace FeO6 octahedra in the n = 3 member Sr4Fe3O10, leading to layered oxycarbonates Sr4Fe3−x(CO3)xO10−4x with 0 < × ≤ 1. Shearing mechanism applied transversally to the layers allows collapsed structures to be generated such as the [Bi2Sr3Fe2O9]n [Bi4Sr6Fe2O16] family and the ferrite Bi13Ba2Sr25Fe13O66. Finally the replacement of rock salt SrO layers in the intergrowth Sr2FeO4 allows a new series of modulated structures [Sr8Fe12O26]·[Sr3Fe2O6]n to be generated, built up of layers of FeO5 bipyramids and tetragonal pyramids intergrown with perovskite layers.