Determination of WSe2 vapor pressure

Evaporation of tungsten diselenide with a hexagonal lattice has been investigated in the temperature range 1100-1300 K in vacuum 1.10-4 mm Hg. Pressure of WSe2 vapour has been determined thermogravimetrically for different temperature and composition of the condensed phase. In a wide composition range the vapour pressure for each temperature monotonically changes within one order of magnitude. Equations have been derived for vapour pressure and evaporation heat of selenium. For compositions containing 30 mass.% of Se and more the heat of evaporation for Se2 is 90800 cal/g. mol