Фазовая диаграмма системы As-Pd

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As-Pd (Arsenic-Palladium) H. Okamoto The equilibrium phases of the As-Pd system are (1) the liquid, L; (2) the rhombohedral terminal solid solution, (As); (3) pyrite-type As2Pd; (4) Fe2P- type bAsPd2; (5) monoclinic aAsPd2; (6) hexagonal As2Pd5, with several stacking variants; (7) hexagonal As3Pd8; (8) Ni3P-type AsPd3; (9) monoclinic AsPd5; and (10) the fcc terminal solid solution, (Pd). The assessed As-Pd phase diagram differs from the diagram of [Shunk], which is based primarily on the work of [64Sai1]. The current diagram is adopted from [ 63Rau], because the diagram of [64Sai1] includes some unlikely features. Basically, the thermal analysis data of [63Rau] and [64Sai] and interpretation of the data disagree considerably in the composition range 60 to 80 at.% Pd. As sublimes at 614 C under 1 atm pressure. The melting point of As is 817 C at 35.8 atm [89Gok]. [63Rau] assumed the homogeneity range of As2Pd to be ~10 at.%. The existence of definite thermal arrests in a 37.5 at.% Pd specimen indicates that the homogeneity range of As2Pd is shown as a line compound [64Sai1]. The "L = As3Pd8 + AsPd3" eutectic temperature appears to be so low as to cause unlikely phase changes in the diagram, i.e., the liquidus boundaries of AsPd3 and As3Pd8 become nearly vertical below ~745 C. [63Rau] did not observe As3Pd8. Therefore, a eutectoid reaction is tentatively shown at 745 C in the assessed diagram. Further clarification is needed. AsPd3 forms by a peritectic reaction at 820 C [63Rau]. Based on two distinctive thermal effects near the melting point, [63Rau] speculated the existence of a certain homogeneity range in AsPd3. Because no other evidence is available, it is shown as a line compound in the assessed diagram. No report is available on the solubility of As in (Pd). [63Rau] observed distinctive thermal effects at 580 and 532 C in the heterogeneous range between 67 and 71 at.% Pd. There are similar unexplained points in the data of [64Sai1]. Existence of other phases and/or impurity effects is possible. AsPd5 with W-type disordered bcc structure forms by splat cooling [83Ell]. [ 83Elb] observed that a glassy phase forms only at ~80 at.% Pd on splat cooling. 29Tho: L. Thomassen, Z. Phys. Chem. B, 4(4), 279-281 (1929) in German. 60Sch: K. Schubert, S. Bhan, W. Burkhardt, R. Gohle, H.G. Meissner, M. Potzschke, and E. Stolz, Naturwissenschaften, 47(13), 303 (1960). 61Hey: R.D. Heyding and L.D. Calvert, Can. J. Chem., 39, 955-957 (1961). 63Rau: Ch.J. Raub and G.W. Webb, J. Less-Common Met., 5, 271-277 (1963). 63Sch: K. Schubert, K. Frank, R. G”hle, A. Maldonado, H.G. Meissner, A. Raman, and W. R”ssteutscher, Naturwissen-schaften, 50(2), 41 (1963) in German. 64Sai1: G.S. Saini, L.D. Calvert, R.D. Heyding, and J.B. Taylor, Can. J. Chem., 42(3), 620-629 (1964). 64Sai2: G.S. Saini, L.D. Calvert, and J.B. Taylor, Can. J. Chem., 42(7), 1511- 1517 (1964). 65Fur: S. Furuseth, K. Selte, and A. Kjekshus, Acta Chem. Scand., 19(3), 735- 741 (1965). 66Ben: S.L. Bennett and R.D. Heyding, Can. J. Chem., 44(12), 3017-3030 (1966). 69Bal: U. Balz and K. Schubert, J. Less-Common Met., 19(3), 300-304 (1969) in German. 74Beg: V.D. Begizov, V.I. Meshchankina, and L.S. Dubakina, Zap Vses. Mineral, Obshch., 103(1), 104-107 (1974) in Russian. 75Cab: L.J. Cabri, J.H.G. Laflamme, J.M. Stewart, J.F. Rowland, and T.T. Chen, Can. Mineralog., 13(4), 321-335 (1975). 78Mat: T. Matkovic and K. Schubert, J. Less-Common Met., 58, P1-P6, (1978) in German. 83Elb: M. El-Boragy, M. Ellner, and B. Predel, Z. Metallkd., 74(8), 545-548 ( 1983) in German. 83Ell: M. Ellner, Z. Kristallogr., 162, 69-71 (1983) in German. 89Gok: N.A. Gokcen, Bull. Alloy Phase Diagrams, 10(1), 11-22 (1989). Submitted to the APD Program. Complete evaluation contains 1 figure, 3 tables, and 18 references. Special Points of the As-Pd System