PREPARATION AND PROCESSING OF RARE-EARTH CHALCOGENIDES

Rare earth chalcogenides are initially prepared by a direct combinatio n of the pure rare earth metal and the pure chalogen element with or w ithout a catalyst. The use of iodine (10 to 100 mg) as a fluxing agent (catalyst), especially to prepare heavy lanthanide chalcogenides, gre atly speeds up the formation of the rare earth chalcogenide. The resul tant powders are consolidated by melting, pressure assisted sintering (PAS), or pressure assisted reaction sintering (PARS) to obtain near t heoretical density solids, Mechanical alloying is a useful technique f or preparing ternary alloys. In addition, mechanical alloying and mech anical milling can be used to form metastable allotropic forms of the yttrium and heavy lanthanide sulfides. Chemical analysis techniques ar e also described because it is strongly recommended that samples prepa red by melting should have their chemical compositions verified becaus e of chalogen losses in the melting step.