The sulfide vapor pressure was measured by using the glass membrane manometer method. It was found that the log[P] versus 1/T curve consisted of 2 straight lines which corresponded to temperature ranges that lay below and above a critical temperature of 740K. The sublimation enthalpy which was deduced from the straight line below the critical temperature was 76.4kcal/mol. This value agreed well with the sublimation enthalpy in the reaction:

CdS(s) ↔ Cd(g) + ½S2(g)

In the case of sublimation at temperatures above the critical value, it was concluded that, in addition to the above reaction, another one:

CdS(s) ↔ (1-x)CdS(s) + ½xS2(g)

occurred and led to sublimation suppression. The activation energy which was necessary in order to create an excess of Cd (a S vacancy) in a CdS crystal was 0.138eV.

Influence of Thermally Created Sulfur Vacancies on Sublimation of Cadmium Sulfide Crystals. J.Nishimura: Japanese Journal of Applied Physics, 1991, 30[3], 537-40