Фазовая диаграмма системы Na-Zn

К оглавлению: Другие диаграммы (Others phase diargams)

Na-Zn (Sodium-Zinc) A.D. Pelton The assessed Na-Zn equilibrium diagram is based on review of the data of [ 06Mat], [68Lam], and [82Mor], and all lines shown are from the current thermodynamic analysis. A wide region of liquid immiscibility extends from 0.8 at.% Zn to 93.5 с 1 at.% Zn at 557 C. One compound, NaZn13, melts at 557 с 5 C, with the formation of two immiscible liquids (syntectic reaction). However, given the error limits of с1 on the composition of L2 at the invariant temperature, the melting could be congruent at 557 C, with a monotectic liquid composition just slightly richer in Na than the compound composition ( 92.9 at.% Zn). The liquidus lines of [06Mat] and [82Mor] agree within about 10 C. The points of [82Mor] agree more closely with the current thermodynamic analysis. The liquidus is very flat in the vicinity of the melting point of the compound, so that the exact composition of L2 at 557 C is difficult to assess precisely. The value of 93.5 at.% Zn is from the thermodynamic analysis. Thermodynamic extrapolation of the liquidus to the melting point of Zn gives a liquidus composition of 99.85 с 0.1 at.% Zn at the eutectic. A thermodynamic freezing point depression calculation using the enthalpy of fusion of Zn from [ 83Cha] gives a eutectic temperature of 418.8 с 0.5 C. Solubilities of Zn in liquid Na were measured over the range 190 to 550 C by [68Lam]. These results agree well with extrapolation, indicating that at 557 C, a solubility of 0.82 at.% Zn is obtained. At 400 C, the solubility is 0.16 at.%. At the melting point of Na, 97.86 C, the solubility is on the order of 10-4 at.% Zn. Hence, the eutectic temperature is indistinguishable from the melting point of pure Na. 06Mat: C.H. Mathewson, Z. Anorg. Chem., 48, 195-200 (1906) in German. 37Ket: J.A.A. Ketelaar, J. Chem. Phys., 5, 668 (1937). 37Zin: E. Zintl and W. Haucke, Naturwissenschaften, 25, 717 (1937) in German. 38Zin: E. Zintl and W. Haucke, Z. Elektrochem., 44, 104-111 (1938) in German. 52Sho: D.P. Shoemaker, R.E. Marsh, F.J. Ewing, and L. Pauling, Acta Crystallogr., 5, 637-644 (1952). 68Lam: G.J. Lamprecht and P. Crowther, Trans. AIME, 242(10), 2169-2171 (1968). 82Mor: A.G. Morachevskii, E.A. Maiorova, and O.I. Vorob'eva, Elektrokhim., 18( 1), 148-150 (1982). 83Cha: M.W. Chase, Bull. Alloy Phase Diagrams, 4(1), 124 (1983). Published in Bull. Alloy Phase Diagrams, 8(6), Dec 1987. Complete evaluation contains 3 figures, 2 tables, and 14 references. 1