Фазовая диаграмма системы La-S

К оглавлению: Другие диаграммы (Others phase diargams)


La-S (Lanthanum-Sulfur) H.F. Franzen The La-S phase diagram is based primarily on the work of [81Kam] and, to a lesser extent, on [78Mir]. In these references, as well as in [87Gsc], the solid solution range of the defect Th3P4-type structure is reported to extend from stoichiometric La3S4 to La2S3. In all three references, the liquidus and solidus curves over this region are reported to exhibit no intermediate congruent melting. A number of authors ([65Cat], [65Gui], [78Mir], [81Kam]) agree that there is no detectable S solubility in LaS; however, [67Bru] reported a metal-rich homogeneity region (0.9 њ S/La њ 1.0) for the monosulfide. The polymorphism in the La2S3 homogeneity range cannot be introduced into the diagram without substantial uncertainty. The high-temperature defect Th3P4- type (g phase) structure [48Zac] is reported to transform to b phase at 1300 C and to a phase at 900 C [73Bes]; however, the fact that the b phase is known to form in other rare-earth sulfides only when oxygen stabilized raises some doubt about the existence of this phase for a pure lanthanum sulfide [ 77Gri]. The report of a 1.33 њ S/La њ 1.41 homogeneity range for La3S4 in the 1400 to 1500 C range [78Gri] suggests the formation of b phase, but the possibility of oxygen stabilization of this phase cannot be ruled out. A high-pressure modification of La2S3 (bLa2S3, P4bm symmetry) [75Ver] and a variety of polysulfides (LaS1.76, tetragonal; LaS1.91, Cu2Sb type; LaS2, NbS2 type; and La3S7) [78Eli] have been reported. 48Zac: W.H. Zachariasen, Acta Crystallogr., 1, 265-268 (1948). 65Cat: E. David Cater, Thomas E. Lee, Ernest W. Johnson, Everett G. Rauh, and Harry A. Eick, J. Phys. Chem., 69(8), 2684-2689 (1965). 65Gui: M. Guittard, C.R. Acad. Sci. Paris, 261, 2109-2112 (1965). 67Bru: G. Bruzzone and G.L. Olcese, Colloq. Int. Cent. Nat. Rech. Sci., 157, 387-395 (1967). 73Bes: P. Besancon, J. Solid State Chem., 7, 232-240 (1973). 75Ver: L.F. Vereshchagin, A.A. Eliseev, G.M. Kuz'micheva, V.V. Evdokimova, V.I. Novokshonov, and O.P. Fialkovski, Russ. J. Inorg. Chem., 20(6), 822-824 (1975) . 77Gri: A.A. Grizik and G.P. Borodulenko, Zh. Neorg. Khim., 22, 542-546 (1977) in Russian; TR: Russ. J. Inorg. Chem., 22(2), 299-301 (1977). 78Eli: A.A. Eliseev, V.A. Tolstova, and G.M Kuz'micheva, Zh. Neorg. Khim., 23, 3171-3180 (1978) in Russian; TR: Russ. J. Inorg. Chem., 23(12), 1759-1764 ( 1978). 78Gri: A.A. Grizik, A.A. Eliseev, V.A. Tolstova, and G.P. Borodulenko, Zh. Neorg. Khim., 23, 595-598 (1978) in Russian. 78Mir: K.E. Mironov, I.G. Vasil'eva, A.A. Kamarzin, V.V. Sokolov, and Yu.N. Maloritskii, Izv. Akad. Nauk SSSR, Neorg. Mater., 14(4), 641-644 (1978) in Russian; TR: Inorg. Mater., 14, 498-501 (1978). 81Kam: A.A. Kamarzin, K.E. Mironov, V.V. Sokolov, Yu.N. Malovitsky, and I.G. Vasil'yeva, J. Cryst. Growth, 52, 619-622 (1981). 87Gsc: K.A. Gschneidner, Jr., J.F. Nakahara, B.J. Beaudry, and T. Takeshita, Mat. Res. Soc. Symp. Proc., 97, 359-369 (1987). Submitted to the APD Program. Complete evaluation contains 1 figure, 1 table, and 18 references. 1