Фазовая диаграмма системы B-Eu

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B-Eu (Boron-Europium) P.K. Liao and K.E. Spear Little experimental work has been performed on the phase equilibria of the Eu- B system. The assessed phase diagram is based primarily on [76Spe]. The equilibrium phases of the Eu-B system are (1) the liquid, L; (2) the terminal solid solution, bcc (Eu); (3) the terminal solid solution, rhombohedral (bB); and (4) one intermediate compound, EuB6. The hexaboride is the only intermediate phase exhibited by the binary Eu-B system, and its observed melting temperature is higher than those of elemental Eu and B. Both (bB) and (Eu) solid solutions have negligible composition ranges. [71Sav] reported that about 0.23 wt.% Eu dissolves in B. Similar to other rare earth hexaborides, EuB6 has a rather wide homogeneity range. A significant effort has gone into investigating the homogeneity ranges and the defect structures of the RE hexaborides [76Spe, 77Spe]. All available experimental data indicate that the hexaboride is stoichiometric at its metal- rich phase boundary and becomes B-rich by the formation of up to approximately 30% metal vacancies [76Spe, 77Spe]. 58Fel: E.J. Felten, I. Binder, and B. Post, J. Am. Chem. Soc., 80, 3479 (1958). 65Gie: R.F. Giese, Jr., J. Economy, and V.I. Matkovich, Z. Kristallogr., 122, 144-147 (1965). 68Mor: O.A. Mordovin and E.N. Timofeeva, Russ. J. Inorg. Chem., 13(2), 1627- 1629 (1968). 70Car: J.-O. Carlsson and T. Lundstrom, J. Less-Common Met., 22, 317-320 (1970) . 71Hac: H. Hacker, Jr., Y. Shimada, and K.S. Chung, Phys. Status Solidi (a), 4, 459-465 (1971). 71Sav: E.M. Savitskii, B.G. Arabei, V.I. Bakarinova, S.E. Salibekov, V.M. Ramashov, and N.I. Timofeeva, Inorg. Mater., 7(4), 539-541 (1971). 73Sch: K. Schwetz and A. Lipp, J. Less-Common Met., 33, 295-303 (1973) in German. 76Spe: K.E. Spear, Phase Diagrams: Materials Science and Technology, Vol. 4, Academic Press, New York, 91-159 (1976). 77Cal: B. Callmer, Acta Crystallogr. B, 33, 1951-1954 (1977). 77Spe: K.E. Spear, Boron and Refractory Borides, Chap. 8, V.I. Matkovich, Ed., Springer-Verlag, New York, 439-456 (1977). 83Pad: Yu.B. Paderno and T. Lundstrom, Acta Chem. Scand., A37, 609-616 (1983). Submitted to the APD Program. Complete evaluation contains 1 figure, 3 tables, and 15 references. Special Points of the Eu-B System