Thermogravimetry study of ion exchange and hydration in layered oxide materials

The behavior in aqueous solutions of the two types of layered perovskite-like structures, NaLnTiO(4) titanates (Ln = Nd, La) belonging to the family of Ruddlesden-Popper phases and ANdTa(2)O(7) tantalates (A = Na, Cs, H) belonging to the family of Dion-Jacobson phases, has been studied by means of thermogravimetric analysis and powder X-ray diffraction. In the case of NaLnTiO(4) compounds, the substitution of protons for sodium cations and the water intercalation into the interlayer space of the crystal structure were observed and proton-containing layered oxides with general formula H (x) Na1-x LnTiO(4)center dot yH(2)O (0.63 < x < 1, 0 < y < 0.74) have been obtained. Investigation on the hydration in layered tantalates ANdTa(2)O(7) (A = H, Na, Cs) showed that NaNdTa2O7 and HNdTa2O7 form compounds intercalated by water molecules. Two steps of water intercalation were observed for NaNdTa2O7 and HNdTa2O7. Stable hydrated compounds HNdTa2O7 center dot 0.84H(2)O, NaNdTa2O7 center dot 0.60H(2)O, and NaNdTa2O7 center dot 1.35H(2)O were synthesized.