Фазовая диаграмма системы B-Y

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B-Y (Boron-Yttrium) P.K. Liao and K.E. Spear Very little experimental work has been done on the phase equilibria for the Y- B system. The assessed equilibrium phase diagram is taken from [77Spe], with review of the work of [61Lun] and [71Oli]. The equilibrium phases are (1) the liquid, L; (2) the terminal solid solutions based on the cph (aY) and bcc (bY); (3) the terminal solid solution based on the b-rhombohedral (B); and (4) five intermediate compounds, YB2, YB4, YB6, YB12, and YB66. (bB) and both (Y) solid solutions have negligible composition ranges. The homogeneity ranges of yttrium borides are small, except perhaps for YB6. Significant effort has gone into investigating the homogeneity ranges of yttrium borides and the hexaboride defect structures. 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]. A variation from stoichiometry of YB12 was reported by [63Joh]. They found this phase could be prepared only with a nonstoichiometric composition of Y0. 92B12. Their density measurements indicated the formation of a metal vacancy defect structure. They attribute their results to the fact that the size of Y is about the maximum for metals that form the dodecaboride phase, and the B lattice must "stretch" to accommodate the yttrium atoms. 54Blu: P. Blum and F. Bertaut, Acta Crystallogr., 7, 81-86 (1954). 58Ste: A.A. Stepanova and N.N. Zhuravlev, Sov. Phys. Crystallogr., 3, 90-91 ( 1958). 61Lap: S. LaPlaca, I. Binder, and B. Post, J. Inorg. Nucl. Chem., 18, 113-117 ( 1961). 61Lun: C.E. Lundin, The Rare Earths, F.H. Spedding and A.H. Daane, Ed., Wiley, New York, 224-385 (1961). 63Joh: R.W. Johnson and A.H. Daane, J. Chem. Phys., 38(2), 425-432 (1963). 65Gie: R.F. Giese, Jr., J. Economy, and V.I. Matkovich, Z. Krist., 122, 144- 147 (1965). 65Mat: V.I. Matkovich, J. Economy, R.F. Giese, Jr., and R. Barrett, Acta Crystallogr., 19, 1056-1057 (1965). 67Mee: G.A. Meerson and F.G. Mamedov, Inorg. Mater., 3(5), 717-721 (1967). 67Pos: B. Post, private communication quoted in [67Hoa]. 69Ric: S.M. Richards and J.S. Kasper, Acta Crystallogr., B25, 237-251 (1969). 70Car: J.-O. Carlsson and T. Lundstrom, J. Less-Common Met., 22, 317-320 (1970) . 71Oli: D.W. Oliver and G.G. Brower, J. Cryst. Growth, 11, 185-190 (1971). 71Pad: Yu.B. Paderno, V.V. Odintsov, I.I. Timofeeva, and L.A. Klochkov, High Temp. 9(1), 175-177 (1971). 72Sch: K. Schwetz, P. Ettmayer, R. Kieffer, and A. Lipp, J. Less-Common Met., 26, 99-104 (1972). 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. Pub. 364, July (1972). 76Spe: K.E. Spear, Phase Diagrams, Vol. IV., Materials Science and Technology, 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, V.I. Matkovich, Ed., Springer- Verlag, Berlin, Heidelberg, New York (1977). Submitted to the APD Program. Complete evaluation contains 1 figure, 3 tables, and 30 references. Special Points of the Y-B System