Stability of Ruddlesden-Popper-structured oxides in humid conditions

Many of the Ruddlesden-Popper-structured A3B2O7−δ oxides readily react with water via intercalation reactions. Three possible factors affecting the water intercalation are identified: oxygen content of the phase, ionic radius of cation A and valence state of cation B. The resultant layered water-derivative phases can be categorised into two groups, depending on the crystal symmetry of the phase.