Sr3Fe2O7 exists in the Ruddlesden-Popper phase with an infinite number of repeating double layers. It is formed from two perovskite layers of linked FeO6 octahedra separated by Strontium cations.
The Ruddlesden–Popper phases of stoichiometry (a) A3B2O7 and (b) A4B3O10, formed respectively from two and three perovskite layers of linked BO6 octahedra separated by A-type cations.