Knudsen measurements of the sublimation and the heat of formation of GeSe₂ [1]

Knudsen effusion studies of the sublimation of polycrystalline GeSe2 have been performed employing mass spectrometry in a temperature range of about 610–750 K and vacuum microbalance techniques in the temperature range 614–801 K and at pressures ranging from about 10−7 − 10−4 atm. The results demonstrate that GeSe2 vaporizes congruently under present experimental conditions according to the predominant reaction (1) GeSe2(s) = GeSe(g) + 1/2 Se2(g) and a minor reaction (2) GeSe2(s) = GeSe2(g). The mean values for the third law heat and second law entropy of reaction (1) based on direct mass‐loss data are ΔH°298 = 70.4 ± 2 kcal/mole and ΔS°298 = 64.7 ± 2 eu. From these the standard heat of formation and absolute entropy of GeSe2(s) were calculated to be −21.7 ± 2 kcal/mole and 24.6 ± 2 eu, respectively. Copyright © 1976 Verlag GmbH & Co. KGaA, Weinheim