Фазовая диаграмма системы Bi-La

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Bi-La (Bismuth-Lanthanum) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed La-Bi phase diagram is based on the work of [77Nom]. They did not determine the form of the phase diagram in the region where the La content exceeded 90 at.%, assuming the coexistence of bLa and gLa with La2Bi. The La-rich compound, La2Bi, forms peritectically at 1252 с 10 C from La5Bi3 and the melt and has a tetragonal structure of the La2Sb-type. The intermediate compound, La5Bi3, also melts incongruently forming La4Bi3 and the melt at 1350 с 20 C. La5Bi3 has a hexagonal structure of the Mn5Si3-type. The only La-Bi compound with a congruent melting point is La4Bi3, which melts at 1670 с 30 C and has a cubic structure of the anti-Th3P4-type. The equiatomic compound, LaBi, decomposes into La4Bi3 and the melt when heated to 1615 с 15 C. LaBi has the cubic NaCl-type structure. [77Nom] reported a peritectic decomposition temperature for LaBi2 at 932 с 10 C. Both an orthorhombic and a triclinic structure have been reported for LaBi2. A eutectic occurs between gLa and La2Bi at 820 C, but the composition in the assessed diagram is probably too high by a factor of 3. [77Nom] reported the coexistence of La2Bi with an unidentified phase in samples containing 75 at.% La that were cooled from 1300 to 750 C in 6 h and from 750 to 100 C in 3 min. This unidentified phase had the I4/mmm space group and a tetragonal unit cell. The observed phase was identified as a tetragonally deformed bcc lattice of gLa, which exists from 865 C to the melting point (918 C). [77Nom] concluded that Bi forms a solid solution with gLa. Averaged solubility data from [61Sch] and [68Kob] indicate that 0.02 at.% La is soluble in Bi at 300 C and 1.2 at.% at 600 C. 61Sch: D.G. Schweitzer and J.R. Weeks, Trans. Quart., 54, 185 (1961). 68Kob: V.I. Kober, V.A. Lebedev, I.F. Nichkov, and S.P. Raspopin, Zh. Fiz. Khim., 42, 686 (1968); TR: Russ. J. Phys. Chem., 42, 360 (1968). 77Nom: K. Nomura, H. Hayakawa, and S. Ono, J. Less-Common Met., 52, 259 (1977). Published in Bull. Alloy Phase Diagrams, 10(4a), Sep 1989. Complete evaluation contains 1 figure, 1 table, and 23 references. 1