ANDERSON PHASES AS PRECURSORS OF NICKEL-MOLYBDENUM-TUNGSTEN OXIDES

Mixed Ni-Mo-W oxides have been prepared by decomposition at 873 K of A nderson-type [NiMo6-xWxO24H6](NH4)(4) . 5H(2)O (x=0, 2, 3, 4, 6) heter opolyoxometallates. Thermal analysis of the precursors, X-ray diffract ion and Raman spectroscopy on the mixed oxides were performed X-Ray po wder patterns, collected at the end of the thermal treatment, revealed that the final products are NiMoO4 and MoO3 for the x=0 composition, whereas for tungsten-containing materials the final products are Mo1-x WxO3 solid solutions, NiWO4 and WO3, depending on the Mo/W atomic rati o. Raman spectra have confirmed the XRPD analysis, revealing the prese nce of a stable WO3-type phase at high molybdenum contents and a high structural stability of Mo1-xWxO3 solid solutions.