Фазовая диаграмма системы K-Te

К оглавлению: Другие диаграммы (Others phase diargams)

K-Te (Potassium-Tellurium) A. Petric and A.D. Pelton The assessed phase diagram is based on [88Pet], who determined liquidus temperatures and temperatures of invariant reactions from 0 to 56 at.% K and 300 to 600 C from discontinuities in the slopes of emf vs temperature or emf vs composition obtained from alloy concentration cells. Discontinuities in the emf curves were observed at 390, 448, and possibly at 484 C, indicating invariant reactions at these temperatures. Because no measurements were made below 300 C, the eutectic reaction shown near 220 C was not directly observed; its position was estimated by extrapolation of the liquidus curves. Evidence for the existence of a compound between K2Te3 and K2Te was obtained by [39Kle], who assigned it the tentative formula KTe because many other alkali chalcogenides of 1:1 stoichiometry have been observed. The observation by [88Pet] of a congruent melting point at the 50 at.% Te composition confirmed this; however, this conclusion is based on only one experimental point and requires verification. Because of the very high melting point of K2Te, and by analogy to many similar systems, the temperature of the eutectic reaction between K2Te and (K) is expected to be indistinguishable from the melting point, 63.71 C, of pure K. The solubility of Te in liquid K at this temperature is expected to be extremely small. Because of the large difference in atomic radius of Te and K, and because of their very different chemical bonding characteristics, there is expected to be negligible solid solubility of K in (Te) or of Te in (K). The limiting slope of the liquidus at 100 at.% Te, when calculated thermodynamically from the enthalpy of fusion of Te under the assumption of negligible solid solubility, agrees very well with the reported limiting liquidus slope in the assessed diagram. 34Zin: E. Zintl, A. Harder, and B. Dauth, Z. Elektrochem., 40, 588-593 (1934) in German. 39Kle: W. Klemm, H. Sodomann, and P. Langmesser, Z. Anorg. Allg. Chem., 241, 281-304 (1939) in German. 78Eis: B. Eisenmann and H. Sch„fer, Angew. Chem. Int. Ed., Engl., 17(9), 684 ( 1978). 88Pet: A. Petric, A.D. Pelton, and M.L. Saboungi, J. Chem. Phys., 85, 5070- 5077 (1988). Submitted to the APD Program. Complete evaluation contains 2 figures, 3 tables, and 8 references. Special Points of the K-Te System