Фазовая диаграмма системы Ag-La

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Ag-La (Silver-Lanthanum) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed Ag-La phase diagram is based primarily on a review of the works of [31Can], [54Vog], [70Mcm], [74Del], and [82Heu]. The data of [74Del] were used to construct the present diagram, with modifications based on the data of [82Heu]. The Ag-rich compound is shown as Ag5La, but is drawn with a dashed line to reflect the uncertainty of this stoichiometry. The compounds Ag3La, Ag2La, and AgLa were reported to exist by [31Can] and [ 54Vog]. [70Mcm] reported the existence of Ag5La and Ag51La14. Ag5La was found to exist in two forms, a low-temperature form with the hexagonal "substituted" MgZn2-type structure and a high-temperature form that was isotypic with Ag5Ce, Ag5Pr, and Ag5Yb. [82Heu] maintained that the correct stoichiometry for this phase was Ag4La. To date, evidence does not conclusively show which composition is correct. In the assessed diagram, Ag5La was tentatively chosen as the appropriate stoichiometry. Structural transformations were studied in an amorphous La-25 at.% Ag alloy prepared by vacuum melting La of purity greater than 99% and spectrographically pure Ag. Quenching produced a noncrystalline structure that remained stable on heating to 150 C. Above 150 C, an irreversible decrease in electrical resistivity occurred. 31Can: G. Canneri, Met. Ital., 23, 803 (1931). 54Vog: R. Vogel and H. Klose, Z. Metallkd., 45, 670 (1954). 70Mcm: O.D. McMasters, K.A. Gschneidner, Jr., and R.F. Venteicher, Acta Crystallogr., B25, 1224 (1970). 74Del: S. Delfino, R. Ferro, R. Capelli, and A. Borsese, Z. Metallkd., 65, 781 (1974). 82Heu: T. Heumann and H. Dirkes, Z. Metallkd., 73, 172 (1982). Published in Bull. Alloy Phase Diagrams, 4(4), Dec 1983. Complete evaluation contains 3 figures, 1 table, and 19 references. 1