Room temperature conversion of X_(0.3)V_2O_5 centre dot nH_2O phase into X_2V_6O_(16) centre dot nH_2O phase Influence of the nature of the cation X~+

摘要

Various cations (Li~+,Na~+,K~+,NH_4~+,Cs~+,Mg~(2+),Ca~(2+),Ba~(2+)) were introduced during the formation of a V_2O_5 centre dot nH_2O gel.Cation intercalated X_y V_2O_5 centre dot nH_2O (y = 0.3 for X = Li~+,Na~+,K~+,NH_4~+ or y = 0.15 for Mg~(2+),Ca~(2+),Ba~(2+)) were first obtained at room temperature but some of them evolve upon ageing into a new phase:XV_3O_8 centre dot nH_2O for X = Na~+,K~+,NH_4~+ and Cs~+ or XV_6O_(16) centre dot nH_2O for X = Mg~(2+),Ca~(2+),Ba~(2+).All the vanadium oxide phases were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and infrared spectroscopy (IR);the supernatant solutions were analysed by ~(51)V NMR spectroscopy.These vanadium oxide phases exhibit a layered structure with cations and water molecules intercalated within the interlayer space.The formation of the different phases depends mainly on the pH of the supernatant solution and on the nature of the cation.