A chemical synthetic route for the preparation of fine-grained metal tungstate powders (M=Ca, Co, Ni, Cu, Zn)

Nanocrystalline metal tungstate [i.e. MWO4 where M=Ca(II),Co(II),Cu(II), Ni(II), and Zn(II)] powders have been prepared from the complete evaporation of a polymer based metal-complex precursor solution. The metal ions are in aqueous solution through complexation with triethanolamine (TEA) and are dispersed in a polymeric reagent composed of an aqueous solution mixture of sucrose and polyvinyl alcohol (PVA). The mesoporous carbon rich precursor powders has been obtained on complete dehydration of the precursor solution and generates the respective metal tungstate phase after complete removal of carbonaceous residue at a heat treatment temperature less than 500°C. X-ray diffractometry (XRD), differential thermal and thermogravimetric analysis (TG/DTA), and transmission electron microscopy (TEM) have been used to characterize the precursors and the heat-treated final powders. The average particle sizes as measured from X-ray line broadening and transmission electron microscopy studies are around ∼15–40 nm. The particles have sizes of the same order to that of crystallite indicate the poor agglomeration of crystallites.