Фазовая диаграмма системы Ge-Mn

К оглавлению: Другие диаграммы (Others phase diargams)

Ge-Mn (Germanium-Manganese) A.B. Gokhale and G.J. Abbaschian The assessed Mn-Ge phase diagram is based primarily on the work of [51Zwi1], [ 51Zwi2], and [69Wac], with review of the data of [51Dow] and [61Oho]. The stable phases include the liquid, L; the four allotropes of the solid solution of Ge in (Mn): (aMn), (bMn), (gMn), and (dMn); the intermediate phases Mn3.4Ge (e), Mn5Ge2 (x), Mn7Ge3 (k), Mn2Ge (c), Mn5Ge3 (h), and Mn3Ge2; and the terminal solid solution of Mn in Ge, (Ge). The system additionally exhibits five eutectics, two peritectics, five allotropic transformations, two eutectoid decompositions, one peritectoid reaction, and two magnetic transitions. The liquidus has been fairly well established. The assessed liquidus is based primarily on the data of [51Zwi2] (0 to 20 at.% Ge), [69Wac] (20 to 100 at.% Ge), and [51Dow] (70 to 100 at.% Ge), whose data were corrected with respect to the melting temperature of pure Ge. Each of the four allotropes of (Mn) forms a solid solution with Ge. The ranges of stability of these solid solutions were determined by [51Zwi2]. According to [51Zwi2], (gMn) forms peritectically from (dMn) + L at 1154 C and approximately 5 at.% Ge. [51Zwi1] indicated the upper limit of stability of ( gMn) to be approximately 13 at.% Ge. The maximum solid solubility of Ge in ( bMn) and (aMn) is ~9 and ~1.5 at.% Ge, respectively [51Zwi2]. Mn3.4Ge (e) is the richest in Mn in the system. This phase melts congruently at 930 C [69Wac], and exhibits two polymorphs: cph (high temperature, e) and fct (low temperature, e1). [61Oho] indicated a homogeneity range of 22 to 23.5 at.% at 800 C. The low-temperature modification undergoes a magnetic transition (Curie point) at 580 C [69Wac]. [69Wac] indicated a eutectoidal decomposition of Mn5Ge2 (x) at 620 C into e1 and Mn7Ge3 (k). The data of [69Wac] are supported by [61Oho], who additionally indicated that the solid state decomposition is very sluggish. [69Wac] established the composition of Mn7Ge3 (k) to be close to 30 at.% Ge, with formation through a peritectoid reaction between x and Mn5Ge3 (h) at approximately 690 C, and a magnetic transition (Curie point) at 420 C. The phase appears to be essentially a line compound. The crystal structure of this phase has not been reported. However, on the basis of the data of [70Lar] for " Mn5Ge2" at a composition represented by Mn2.3Ge, the phase appears to be orthorhombic. Mn5Ge3 (h) melts congruently at 966 C [69Wac] and possibly undergoes a second- order transformation (h = h›) by atomic rearrangement at 776 C [70Gup]. The homogeneity range for h has not been determined. [60Tru] indicated the equilibrium distribution coefficient (K = Xs/X1) of Mn in Ge at the melting point of Ge to be ~10-6. Based on this value and the data of [69Wac], the solid solubility of Mn in (Ge) appears to be negligible. [75Gud] investigated metastable phase formation in Ge-Mn by quenching liquid alloys to form ribbons with reported cooling rates of 107 to 108 C/s. Their results were based on nine alloys ranging in composition from 0 to 27 at.% Ge. They reported a metastable extension in the solid solubility of (gMn) up to ~ 20 at.% Ge, with a change in the crystal lattice from fct (low Ge) to fcc ( high Ge). The crystal lattice change is similar to that observed under equilibrium conditions by [51Zwi1]. The lattice change was apparently noncontinuous because both types were detected at intermediate compositions. An alternative phase was found to crystallize in the bcc lattice, denoted by ( bcc)m, in place of the equilibrium phase e. However, even under the rapid cooling rates employed, the equilibrium x phase was found to be present at its stoichiometric composition. The formation of amorphous films obtained by sputter deposition has been reported for Mn3Ge2 [78Ale, 81Hau], MnGe [81Hau], and Mn11Ge8 [78Ale]. 49Zwi: V. Zwicker, E. Jahn, and K. Schubert, Z. Metallkd., 40(12), 433-436 ( 1949) in German. 51Dow: J.H. Downing and D. Cubicciotti, J. Am. Chem. Soc., 73(8), 4025 (1951). 51Zwi1: V. Zwicker, Z. Metallkd., 42, 246-252 (1951) in German. 51Zwi2: V. Zwicker, Z. Metallkd., 42, 327-330 (1951) in German. 60Tru: F.A. Trumbore, Bell System Tech. J., 39, 205-233 (1960). 61Oho: T. Ohoyama, J. Phys. Soc. Jpn., 16(10), 1995-2002 (1961). 69Wac: E. Wachtel and E.T. Henig, Z. Metallkd., 60(3), 243-247 (1969) in German. 70Gup: S.K. Gupta and K.P. Gupta, J. Less-Common Met., 20, 1-6 (1970). 70Lar: M. Laridjani, M. Bigare, and A. Guinier, Mem. Sci. Rev. Met., 67(10), 675-679 (1970) in French. 71Kad: G. Kadar and E. Kren, Int. J. Magn., 1, 143-148 (1971). 74Isr: P. Israiloff, H. Vollenkle, and A. Wittmann, Monatsh. Chem., 105, 1387- 1404 (1974) in German. 75Gud: V.N. Gudzenko and A.F. Poleysa, Russ. Metall., 5, 153-156 (1975). 78Ale: Yu.S. Alekseev, E.S. Levin, and G.V. Geld, Fiz. Tverd. Tela, 20, 2742- 2745 (1978) in Russian; TR: Sov. Phys. Solid State, 20(9), 1582-1584 (1978). 80Ell: M. Ellner, J. Appl. Crystallogr., 13, 99-100 (1980) in German. 81Hau: J.J. Hauser and F.S.L. Hsu, Phys. Rev. B., 24(3), 1550-1551 (1981). 81Kom: Y. Komura and H. Hirayama, Acta Crystallogr. A, 37 (Suppl.), C184-C185 ( 1981). Submitted to the APD Program. Complete evaluation contains 4 figures, 4 tables, and 47 references. Special Points of the Mn-Ge System