SOLID-STATE METATHESIS AS A QUICK ROUTE TO TRANSITION-METAL MIXED DICHALCOGENIDES

Solid-solution transition-metal dichalcogenides, traditionally synthesized from the elements at elevated temperatures over long periods of time, can now be prepared from rapid self-propagating reactions between transition-metal halides and alkali-metal mixed chalcogenides such as Na2(S,Se). The transition-metal dichalcogenide solid solution is isolated by simply washing away the byproduct salt. Powder X-ray diffraction and thermogravimetric analyses of the solid solutions Mo(S,Se)2 and W(S,Se)2 are presented. Although any composition can theoretically be prepared, the stoichiometry of the product is influenced by the temperatures attained during the course of the reaction. The products are characteristically enriched in the more volatile non-metal component relative to the alkali-metal mixed-chalcogenide precursor. The observed kinetic products and selective enrichment suggest that elemental intermediates may be involved in these reactions.