Фазовая диаграмма системы Ce-Si

К оглавлению: Другие диаграммы (Others phase diargams)

Ce-Si (Cerium-Silicon) A. Munitz, A.B. Gokhale, and G.J. Abbaschian The Ce-Si system is characterized by the presence of six intermediate phases-Ce5Si3, Ce3Si2, Ce5Si4, CeSi, Ce3Si5, and CeSi2. Six eutectic reactions and a peritectic reaction occur: (1) L = Ce + Ce5Si3 at 8 at.% Si and 650 C; ( 2) L = Ce5Si3 + Ce3Si2 at 38.5 at.% Si and 1270 C; (3) L = Ce3Si2 + Ce5Si4 at 42 at.% Si and 1360 C; (4) L = Ce5Si4 + CeSi at 46 at.% Si and 1390 C (not determined reliably, according to [74Gsc]; (5) L = CeSi + Ce3Si5 at 53 at.% Si and 1400 C (assumed in this evaluation); (6) L + CeSi2 = Ce3Si5 at about 61.5 at.% and 1560 C; and (7) L = CeSi2 + Si at 87 at.% Si and 1200 C. The assessed diagram is based primarily on the work of [66Ben] and was obtained by use of a thermodynamic model based on [77Rys]. The diagram of [ 66Ben] was later modified by [74Gsc] and subsequently by [Moffatt]. The present evaluators have further modified the diagram by changing the melting temperatures of Ce and Si and the d = g transformation temperature of Ce to the currently accepted values [Gschneidner]. In addition, the g = b transformation for Ce has been included, and the portion of the diagram between 60 and 70 at.% Si has been modified. The liquidus in the system is mostly undetermined and hence is indicated by dashed lines. There are no reliable solid solubility data available in the literature. [ 66Ben] rather speculatively indicated a small (1.2 at.%) range of mutual solid solubility. However, the mutual solid solubility is probably negligible. The present evaluators have based this estimate on the fact that in other RE-Si binary systems the mutual solid solubilities are very small. The presence of two other intermediate phases was mentioned in the literature. [65Dvo] suggested the presence of Ce3Si, and [56Bre] reported a phase corresponding to the composition CeSi0.75 (Ce4Si3). Because there are no other sources supporting the existence of these phases, the present evaluators have excluded them from the assessed equilibrium diagram. [66Ben] reported the presence of two intermediate phases-CeSi2-x (indicating Si deficiency, x not specified) and CeSi2-in the composition range 60 to 70 at. % Si. However, crystallographic data presented later indicated that the phases may be CeSi2, with the aThSi2-type structure and a homogeneity range of 64 to 66.67 at.% Si, and Ce3Si5, with the aGdSi2-type structure. The presence of a homogeneity range for CeSi2 and the existence of another phase are also supported by the work of [82Yas]; their data on magnetic transitions showed that in the range 64 to 66.67 at.% Si the phase is nonmagnetic, whereas a sharp magnetic transition was observed at compositions below 64 at.% Si. According to [63Mat], CeSi2 does not exhibit a superconducting transition down to temperatures ~1 K. 56Bre: L. Brewer and D. Krikorian, J. Electrochem. Soc., 103(38-51), 701-703 ( 1956). 63Mat: B.T. Matthias, T.H. Gaballe, and V.B. Compton, Rev. Mod. Phys., 35(1), 1-22 (1963). 64Gla: E.I. Gladyshevskii, Izv. Nauk, 141-143 (1964) in Russian; TR: U.S. Dept. Comm. JPRS-28849, 184-187 (1964). 64Rug: A.F. Ruggiero and G.L. Olcese, Atti Accad. Naz. Lincei, Rend., 37, 169- 174 (1964). 65Dvo: L.A. Dvorina, Izv. Akad. Nauk SSSR, Neorg. Mater., 1(10), 1772-1777 ( 1965) in Russian; TR: Inorg. Mater., 1, 1604-1608 (1965). 66Ben: F. Benesovsky, H. Nowotny, W. Pifger, and H. Rassaerts, Monatsh. Chem., 97, 221-229 (1966) in German. 67Smi: G.S. Smith, A.G. Tharp, and Q. Johnson, Acta Crystallogr., 22, 940-943 ( 1967). 72May: I. Mayer and I. Felner, J. Less-Common Met., 29, 25-31 (1972). 74Gsc: K.A. Gschneidner, Jr. and M.E. Verkade, Selected Cerium Phase Diagrams, Doc. IS-RIC-7, Iowa State University, Ames, 36-37 (1974). 77Rys: G.M. Ryss, Yu.O. Esin, A.I. Stroganov, and P.V. Geld, Zh. Fiz. Khim., 51, 232-233 (1977) in Russian; TR: Russ. J. Phys. Chem., 51(1), 134-135 (1977). 82Yas: H. Yashima, T. Satoh, H. Mori, D. Watanage, and T. Ohtsuka, Solid State Commun., 41(1), 1-4 (1982). Published in Bull. Alloy Phase Diagrams, 10(1), Feb 1989. Complete evaluation contains 3 figures, 5 tables, and 31 references. 1