Фазовая диаграмма системы Fe-Se

К оглавлению: Другие диаграммы (Others phase diargams)

Fe-Se (Iron-Selenium) H. Okamoto The assessed Fe-Se phase diagram is based mainly on [68Dut2] (0 to 45 and 60 to 100 at.% Se) and [79Sch] (45 to 60 at.% Se). The equilibrium phases are (1) the liquid, L (L1, L2, and L3); (2) the bcc terminal solid solution, (dFe); (3) the fcc terminal solid solution, (gFe); (4) the bcc terminal solid solution, ( aFe); (5) tetragonal PbO-type b; (6) high-temperature d›; (7) hexagonal NiAs- type d; (8) monoclinic g›; (9) monoclinic g; (10) two allotropic forms of Fe7Se8, with poorly defined phase relationships; (11) orthorhombic FeS2( marcasite)-type e; and (12) the hexagonal terminal solid solution, (gSe). The Fe-rich monotectic reaction was reported at substantially different temperatures by [61Tro] and [67Kul] (~960 C) and by [68Dut2] (1520 C). According to [61Tro] and [67Kul], the miscibility gap at the monotectic temperature occurs between ~6.5 and 46.0 at.% Se, and the L = (Fe) + d eutectic is at 5.5 at.% Se and 940 C. Accordingly, the initial slope of the ( dFe) liquidus is about -100 C/at.%. However, the maximum possible slope is -20 C/at.%, assuming no solubility of Se in (dFe) and 13 800 J/mol [83Cha] for the heat of fusion. Therefore, the result of [68Dut2] is accepted in the assessed diagram. Further studies are needed, because [68Dut2] observed a mysterious thermal effect at 1490 C, and the form of the miscibility gap is unknown. The Se-rich miscibility gap was determined by [68Dut2]. No solid solubility of Se in Fe phases was detected [67Kul, 68Dut2, 78Jai]. Two forms of Fe7Se8 (53.3 at.% Se) exist, but the phase relationships among these modifications of Fe7Se8 and other phases are nebulous, due to the hysteresis in transition processes. The solubility of Fe in liquid Se is 0.04 at.% at 790 C [68Dut1]. A thin-film metastable FeSe grown by codeposition of Fe and Se has a cubic structure [75Sri], which transforms to a hexagonal phase on annealing at 150 to 200 C. This hexagonal phase resembles the stable NiAs-type d, but the lattice parameters are considerably different. On further annealing in the temperature range 250 to 300 C, the hexagonal phase transforms to a tetragonal AuCu-type phase [75Sri]. A pyrite-type FeSe2 compound forms under high pressure (65 kbar) and high temperature (800 to 1200 C) [66Bit, 68Bit]. The Curie temperature (Tc) of pure aFe is 770 C [82Swa]. d is antiferromagnetic or ferrimagnetic, depending on the composition [78Ter2]. The N‚el temperature decreases with increasing Se content from -64 C at 51.98 at.% Se to -143 C at 53.35 at.% Se [78Ter2]. The Curie temperature of ferrimagnetic d is about 150 [54Hir] or 180 C [56Hir, 78Ter1] between ~51 and ~60 at.% Se and decreases with increasing Se content to about 30 C at 57.5 at. % Se [54Hir] or at 58.5 at.% Se [78Ter1]. The ferrimagnetic Curie temperatures of the high- and low-temperature modifications of Fe7Se8 are 189 and 187 C, respectively [61Oka]. [67Kaw] investigated the magnetic structures of these modifications. 54Hir: T. Hirone, S. Maeda, and N. Tsuya, J. Phys. Soc. Jpn., 9(4), 496-499 ( 1954). 56Hir: T. Hirone and S. Chiba, J. Phys. Soc. Jpn., 11(6), 666-670 (1956). 61Oka: A. Okazaki, J. Phys. Soc. Jpn., 16(6), 1162-1170 (1961). 61Tro: P. Troften and G. Kullerud, Carnegie Inst. Wash. Year Book, 60, 176 ( 1961). 66Bit: T.A. Bither, C.T. Prewitt, J.L. Gillson, P.E. Bierstedt, R.B. Flippen, and H.S. Young, Solid State Commun., 4(10), 533-535 (1966). 67Kaw: M. Kawaminami and A. Okazaki, J. Phys. Soc. Jpn., 22, 924 (1967). 67Kul: G. Kullerud, Carnegie Inst. Wash. Year Book, 67, 175-177 (1967-1968). 68Bit: T.A. Bither, C.T. Prewitt, J.L. Gilson, P.E. Bierstedt, R.B. Flippen, and H.S. Young, Inorg. Chem., 7, 2208-2210 (1968). 68Dut1: J.E. Dutrizac, M.B.I. Janjua, and J.M. Toguri, Can. Metall. Q., 7(2), 91-92 (1968). 68Dut2: J.E. Dutrizac, M.B.I. Janjua, and J.M. Toguri, Can. J. Chem., 46(8), 1171-1174 (1968). 75Sri: M.M. Srivastava and N.O. Srivastava, Thin Solid Films, 29(2), 275-284 ( 1975). 78Jai: B.K. Jain, A.K. Singh, and K. Chandra, J. Phys. F. Met. Phys., 8(12), 2625-2630 (1978). 78Ter1: P. Terzieff and K.L. Komarek, Monatsh. Chem., 109(3), 651-659 (1978). 78Ter2: P. Terzieff and K.L. Komarek, Monatsh. Chem., 109(5), 1037-1047 (1978). 79Sch: W. Schuster, H. Mikler, and K.L. Komarek, Monatsh. Chem., 110(5), 1153- 1170 (1979). 82Swa: L.J. Swartzendruber, Bull. Alloy Phase Diagrams, 3(2), 161-165 (1982). 83Cha: M.W. Chase, Bull. Alloy Phase Diagrams, 4(1), 123-124 (1983). Submitted to the APD Program. Complete evaluation contains 1 figure, 3 tables, and 50 references. Special Points of the Fe-Se System