Sulfur Nonstoichiometry of PrS2: A Series of New Sulfur-Deficient Phases

A series of new sulfur-deficient polysulfides, PrS1.900 (2), PrS1.846 (6), PrS1.766 (8), and PrS1.702 (7), in addition to stoichiometric PrS2, has been found by the detailed study of the PrS2–PrS1.5 system in the temperature range 350–1000°C. The phase individuality of the polysulfides has been proved on the basis of data of a sensitive static tensimetric method with a quartz Bourdon gauge, X-ray single-crystal structure analysis, and Raman spectroscopy. The vapor pressure and evaporation thermodynamic parameters of the polysulfides have been determined. Information on a structural distortion of the (S2-2)polyanionic fragment in the sulfur-deficient phases has been extracted from the Raman spectra components assigned to vibrations of this fragment.