Фазовая диаграмма системы B-Yb

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B-Yb (Boron-Ytterbium) P.K. Liao and K.E. Spear Phase equilibria studies on the Yb-B system are quite limited. The assessed phase diagram is from [76Spe] and is largely estimated. Even though many of the temperatures and compositions shown are very uncertain, the general diagram is of the type to be expected. The volatile nature of the Yb metal ( low normal boiling temperature, high vapor pressure) cause the 1-atm vapor phase to play a major role in the assessed diagram. The equilibrium condensed phases are (1) the liquid, L; (2) the terminal solid solutions, bcc (gYb) and fcc (bYb); (3) the terminal solid solution, rhombohedral (bB); and (4) five intermediate compounds, YbB2, YbB4, YbB6, YbB12, and YbB66. (bB) and (gYb) solid solutions have negligible composition ranges. The melting behavior and corresponding melting temperatures of the Yb borides have been measured for only YbB6 and YbB66. [68Mor] reported a melting temperature of 2370 C for YbB6, but did not state the mode of melting (or decomposition). In studies of seven REB66 compounds, including YbB66, [72Spe] determined that all the REB66 phases melt at approximately 2150 с 100 C. The decomposition mechanisms of the Yb boride phases were predicted by [76Spe] from trends correlated for the RE boride systems. The homogeneity ranges of Yb borides are expected to be small, except for the YbB6 phase. The rather wide homogeneity ranges for a number of REB6 phases were discussed by [76Spe]. 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. 56Pos: B. Post, D. Moskowitz, and F.W. Glaser, J. Am. Chem. Soc., 78, 1800- 1802 (1956). 59Eic: H.A. Eick and P.W. Gilles, J. Am. Chem. Soc., 81, 5030-5032 (1959). 63Lap: S. LaPlaca, D. Noonan, and B. Post, Acta Crystallogr., 16, 1182 (1963). 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(12), 1627- 1629 (1968). 70Car: J.-O. Carlsson and T. Lundstrom, J. Less-Common Met., 22, 317-320 (1970) . 70Eto: J. Etourneau, J.-P. Mercurio, R. Naslain, and P. Hagenmuller, J. Solid State Chem., 2, 332-342 (1970) in French. 71Odi: V.V. Odintsov and Yu.B. Paderno, Inorg. Mater., 7(2), 294 (1971). 71Pad: Yu.B. Paderno, V.V. Odintsov, I.I. Timofeeva, and L.A. Klochkov, High Temp., 9(1), 175-177 (1971). 72Fis: Z. Fisk, A.S. Cooper, P.H. Schmidt, and R.N. Castellano, Mater. Res. Bull., 7(4), 285-288 (1972). 72Sch: K. Schwetz, P. Ettmayer, R. Kieffer, and A. Lipp, J. Less-Common Met., 26, 99-104 (1972) in German. 72Spe: K.E. Spear and G.I. Solovyev, Solid State Chemistry, Proc. 5th Mater. Res. Symp., R.S. Roth and S.J. Schneider, Ed., NBS Spec. Publ. 364, Jul (1972). 74Bau: J. Bauer, C.R. Acad. Sci. Paris, Ser. C, 279, 501-504 (1974) in French. 76Spe: K.E. Spear, Phase Diagrams, Vol. 4, Materials Science and Technology, Academic Press, New York, 91-159 (1976). 77Cal: B. Callmer, Acta Crystallogr. B, 33, 1951-1954 (1977). Submitted to the APD Program. Complete evaluation contains 1 figure, 3 tables, and 21 references. Special Points of the Yb-B System