Alkaline earth titanoniobates with a layer structure : A0.5H(TiNbO5)2.nH2O |
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| Authors: | A. Grandin M.M. Borel B. Raveau |
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| Affiliation: | Laboratoire de Cristallographie, Chimie et Physique des Solides, U.A. 251 ISMRa-Université, 14032 Caen Cedex, France |
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| Abstract: | The ion exchange properties of the layer oxide HTiNbO5 in the presence of alkaline earth acetate solution A(CH3COO)2 has been investigated. The maximum exchange rate increases with the size of the A ion, leading to the hydrates : Ba(TiNbO5)2.4H2O, Sr0.75H0.50(TiNbO5)2.4H2O and Ca0.50H(TiNbO5)2.4H2O. The minimum exchange rate corresponds to the definite compounds A0.5H(TiNbO5)2.4H2O, labelled 4W-hydrates. The study of the thermal stability of the 4W-hydrates leads to the hydrates A0.5H(TiNbO5)2.2H2O and A0.5H(TiNbO5)2.H2O, and finally to the dehydrated oxides A0.5H(TiNbO5)2. The reversibility of the ion exchange reaction and of the hydration phenomenon has been studied. The X-ray diffraction study of these compounds shows that the structure of the (TiNbO5) layers is conserved whatever the nature of the A ion and of the hydrate may be. The structural evolution versus water content and size of the A ions is discussed. |
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