Vapor pressure of indium chloride and some implications for the In-Se system
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Section I: Basic and Applied Research
Vapor Pressure of Indium Chloride and Some Implications for the In-Se System Robert F. Brebrick
(Submitted August 18, 2003; in revised form October 18, 2004) The optical absorbance of the vapor over InCl in the ultraviolet spectrum was measured. Comparison with the published vapor pressure yields a Beer’s law constant of 0.00143 atm-cm for the 267.6 nm peak, and a 1273 K optical path. The spectrum is found to match unidentified peaks found in a recent study of the In-Se system. The amount of InCl in the In-Se samples of the recent study was calculated and was found to be by weight and of negligible influence on the partial pressures obtained there. However, on the basis of the results obtained here and on those from the recent study of the In-Se system, it appears likely that the published partial pressure of the subselenide over 33.3 at.%Se (In-Se) is in error and is actually that of an InCl impurity.
1. Introduction The current study yields information on the In-Cl system and enables the resolution of some ambiguities in a recent extensive study (Ref 1) of the In-Se system. The spectrum of InCl(g) in the ultraviolet range was obtained, and, using the published vapor pressure of InCl(s), the Beer’s law constants for the InCl(g) peaks were established. These include the strong 266.6 and 267.6 nm peaks. A comparison of the InCl(g) spectrum with unidentified peaks observed in the In-Se study (Ref 1) shows that the latter are due to InCl(g). (See the 266.6 and 267.6 nm peaks in Fig. 4 of Ref 1.) Although the InCl(g) peaks were easily observed in the In-Se study, one can now conclude the total weight of InCl(g) present was most likely to be too low to affect the partial pressures of Se2(g) and In2Se(g) that were measured. Moreover, measurements on one of the two pure In sources used in the In-Se study also showed the presence of InCl(g) and so established the In as the source of the impurity. Finally, the discrepancy between the results of Ref 1 and a determination of the total pressure over 33.3 at.%Se (In-Se system) now seems likely to be due to the erroneous identification of InCl(g) as In2Se in the total pressure study.
2. Experimental InCl3 was synthesized by dissolving In in HCl, evaporating it to dryness, then subliming the material at 660 K in a vacuum of about 10−6 atm. Then 0.126 g of the white trichloride flakes and 0.139 g of In were sealed in a Tshaped optical cell of fused silica at about 10−9 atm. These weights correspond to slightly more than 2 mol of In per mole of the trichloride, enough to give InCl + In on complete reaction. The optical cell, furnace, and general proce-
R.F. Brebrick, Professor Emeritus College of Engineering, Marquette University, Milwaukee, WI 53233. Contact e-mail: rbrebrick@ milwpc.com.
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dure were the same as those used in the previous study (Ref 1). A 15.2 cm long evacuated cell was placed against either side of the T-shaped optical cell to displace hot air from the optical path. The path of the optical cell containing the sample wa
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