Synthesis, structure, and properties of ammonium polyvanadomolybdate xerogels

Powders and films of (NH4)(2-x)HxV12-yMoyO31+delta . nH(2)O (0 less than or equal to x less than or equal to 2, 0 less than or equal to y less than or equal to 3) xerogels with a layered structure were prepared for the first time. According to IR spectroscopy data, the V-O-Mo layers in the xerogels are similar to those in the delta vanadium bronze (NH4)(0.5)V2O5. X-ray pho toelectron spectroscopy shows that the vanadium and molybdenum in the xerog els are mainly in the oxidation states 5+ and 6+, respectively. The materia ls also contain small amounts of V4+ and OH-. The thermal stability of the materials increases with Mo content. The electrical conductivity of the fil ms depends on air humidity and reaches a maximum at the composition (NH4)(1 .5)H0.5V9Mo3O31+delta . nH(2)O. At temperatures in the range 20-70 degreesC and air humidity between 12 and 59%, the activation energy of conduction i s very low.