Фазовая диаграмма системы Ir-Li

К оглавлению: Другие диаграммы (Others phase diargams)

Ir-Li (Iridium-Lithium) J. Sangster and A.D. Pelton The assessed phase diagram for the Li-Ir system is tentative and was calculated thermodynamically on the basis of very sparse data and by analogy with the Li-Rh system. The compound LiIr was prepared by direct combination of the elements in iron [ 64Mag, 78Var] or molybdenum [76Don] containers and characterized by X-ray diffraction. The small variation in the lattice parameter between the Li-rich and Ir-rich composition limits [76Don] indicates a narrow but measurable range of homogeneity. In two thermal analysis experiments in which LiIr was heated rapidly, it was observed [64Mag] to melt in the range 2080 to 2120 C. Details are lacking, but it seems that the samples were heated in vacuo. Li losses by decomposition were cited to explain the range of measured melting points. A congruent melting point of 2100 C or higher for LiIr was thus proposed by [ 64Mag] and [78Var]. A congruent point of 2120 C is shown in the assessed diagram. When 4:1 and 1:4 molar ratios of Li and Ir were heated in vacuo at 700 C for 24 h, the X-ray diffraction patterns showed only LiIr and either excess Li or excess Ir. However, by reacting the elements in sealed molybdenum capsules at 800 C for 7 days, [76Don] produced the compound LiIr3, which they characterized by X-ray diffraction. The work appears to have been carefully performed. The small variation in lattice parameter between the Li-rich and Ir- rich composition limits indicates a narrow but measurable range of homogeneity. [76Don] produced the compound LiRh3, which they showed to be isotypic with LiIr3. The existence of LiIr3 thus appears to be well established. Its melting behavior is unknown. Behavior is expected to be similar to the Li-Rh system. Because LiIr has a higher melting point than LiRh (which melts at ~1890 C [64Mag]), the eutectic temperature in the Li-Ir system is probably even closer to the melting point of pure Li, and the eutectic liquid composition probably lies at <0.1 at.% Ir. 64Mag: C.B. Magee, Final Report to the Joint US EURATOM Research and Development Program, Contract No. AT(11-1)-1185, Denver Res. Inst., Univ. Denver (AEC Accession No. 4583, DRI-2184) (1964). 76Don: H.C. Donkersloot and J.H.N. Van Vucht, J. Less-Common Met., 50(2), 279- 282 (1976). 78Var: S.K. Varma, F.C. Chang, and C.B. Magee, J. Less-Common Met., 60(2), P47- P63 (1978). Submitted to the APD Program. Complete evaluation contains 1 figure, 1 table, and 5 references. 1