Structural study of gels of V2O5: Vibrational spectra of xerogels

A complete vibrational study of xerogels of vanadium oxide corresponding to the formula V/sub 2/O/sub 5/ x nH/sub 2/O with n = 1.6, 1.2, 0.6, 0.4, and 0.3, was performed. Raman and infrared spectra of powder and oriented films of the samples have been recorded at 100 and 300 K. It has been possible to verify the existence of two different structures. For n = 0.3, V/sub 2/O/sub 5/ layers are connected as in the crystal through V=O-V bonds, each water molecule trapped into cavities being linked by its two hydrogen atoms to the oxygen lattice, the interlayer distance (b parameter) should be close to that of the crystal. For n = 0.6, the V/sub 2/O/sub 5/ layers are not connected as in the crystal through the long V-O bonds, but the vanadium atoms are coordinated to H/sub 2/O molecule by V-OH/sub 2/ bonds. For 0.6 < n < 1.4 three kinds of water molecules are likely present. Finally, it is shown that the conclusions are consistent with the literature structural models proposed from diffraction methods. 18 references, 9 figures, 2 tables.