Фазовая диаграмма системы Ag-Ge

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Ag-Ge (Silver-Germanium) R.W. Olesinski and G.J. Abbaschian The equilibrium phases of the Ge-Ag system are (1) the liquid, L; (2) the solid solution, (Ge), with negligible solubility of Ag; and (3) the terminal solid solution, (Ag), with a maximum solubility of 9.6 at.% Ge at the eutectic temperature (651 C). The solid solubility of Ag in (Ge) is retrograde, with a maximum of 0.009 at.% Ag at about 800 C [62Kos]. The assessed phase diagram, which is a simple eutectic, is based on the experimental data of [29Bri], [36Mau], [40Owe], and [62Kos]. There is good agreement between the experimentally determined liquidus and the liquidus obtained by thermodynamic optimization of the enthalpy of mixing data of [ 83Has]. Independently, [88Che] assessed the Ag-Ge phase diagram thermodynamically. A metastable cph phase occurs in rapidly solidified alloys [60Duw, 61Kle, 64Mos]. The lower limit of the melt composition required for the formation of this phase is around 15 at.% Ge, and its homogeneity range is estimated to be 77 to 80 at.% Ag [77Aga]. A tetragonal metastable phase was reported in splat-cooled alloys containing 79 at.% Ag [69Ram], but its identification remains rather uncertain. Also, rapid quenching of super-heated alloys resulted in extension of the solid solubility of Ge in (Ag) to around 20 at.% Ge [77Aga]. The composition of (Ge) can be extended to 5 at.% Ag in crystalline films obtained at 450 C and to about 10 at.% Ag in films crystallized upon heating of the amorphous films at the same temperature. Studies of splat-cooled samples by [77Aga] showed that, in an alloy containing 77.5 at.% Ag, small amounts of an amorphous phase were formed apart from the cph phase. 29Bri: T.R. Briggs, R.O. McDuffie, and L.H. Willisford, J. Phys. Chem., 33, 1080-1096 (1929). 36Mau: H. Maucher, Forschungsarb. Metallkd. Rontgenmetal., 20, 1-32 (1936) in German. 40Owe: E.A. Owen and V.W. Rowlands, J. Inst. Met., 66, 361-378 (1940). 60Duw: P. Duwez, R.H. Willens, and W. Klement, Jr., J. Appl. Phys., 31, 1137 ( 1960). 61Kle: W. Klement, Jr., J. Inst. Met., 90, 27-30 (1961). 62Kos: V.E. Kosenko, Sov. Phys. Solid State, 4, 42-43 (1962). 64Mos: M. Moss, D.L. Smith, and R.A. Lefever, Appl. Phys. Lett., 5, 120-121 ( 1964). 69Ram: P. Ramachandrarao and T.R. Anantharaman, Trans. AIME, 245, 886-887 ( 1969). 77Aga: S.C. Agarwal and H. Herman, J. Mater. Sci., 12, 2021-2027 (1977). 83Has: S. Hassam, M. Gaune-Escard, and J.P. Bros, High Temp. Sci., 16(2), 131- 151 (1983). 88Che: P.Y. Chevalier, Thermochim. Acta, 130, 25-32 (1988). Published in Bull. Alloy Phase Diagrams 9(1), Feb 1988. Complete evaluation contains 2 figures, 4 tables, and 42 references. 1