Фазовая диаграмма системы Au-Cs

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Au-Cs (Gold-Cesium) A.D. Pelton The Au-Cs system is characterized by the presence of one compound, AuCs, that has been definitely well established. It is not clear whether it forms by congruent or incongruent melting. The existence of the compound Au5Cs has been proposed by [79Esc], [81Kem], and [81Som], based on thermal analysis and by analogy with the compounds Au5K and Au5Rb. The assessed phase diagram is based primarily on the work of these authors, with review of the work of [61Kie]. Error limits of at least 50 C should be placed on the assessed liquidus at Cs concentrations above 75 at.%. A eutectic reaction was reported at 27 C by [61Kie]. Under the assumption of negligible solubility of Au in (Cs), a liquid composition of 99.6 at.% Cs at the eutectic temperature was calculated from the enthalpy of fusion and melting point of pure Cs (28.39 C). However, from the thermodynamically extrapolated liquidus in the assessed diagram, a much lower solubility of Au in liquid Cs at this temperature is calculated, so that a eutectic temperature virtually identical to the melting point of Cs is predicted. The Au-Cs system is effectively split into two subsystems. The AuCs-Cs subsystem can be considered similiar to the other metal-molten salt systems- CsF-Cs, CsCl-Cs, and CsI-Cs. All exhibit liquidus curves indicative of a tendency to immiscibility and positive deviations from ideality in the liquid state. The Au-AuCs subsystem has a metallic and an ionic constituent, and therefore, positive deviations from ideality also are expected. 61Kie: G. Kienast and J. Verma, Z. Anorg. Allg. Chem., 310, 143-169 (1961) in German. 79Esc: D. Eschenweck, Ph.D. dissertation, University of Stuttgart (1979) in German. 81Kem: A. Kempf, Ph.D. dissertion, University of Marburg, Germany (1981) in German. 81Som: F. Sommer, D. Eschenweck, B. Predel, and R.W. Schmutzler, Chemical Metallurgy-A Tribute to Carl Wagner, AIME, Warrendale, PA 19-27 (1981). Published in Phase Diagrams of Binary Gold Alloys, 1987, and Bull. Alloy Phase Diagrams, 7(1), Feb 1986. Complete evaluation contains 3 figures, 2 tables, and 14 references. 1