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Phase Diagram Evaluations: Section II

Fe-Gd-Sn (Iron-Gadolinium-Tin) V. Raghavan

Recently, [2004Mud] determined a composite isothermal section for this system at 597
C for 55 at.% Sn.

Binary Systems The Fe-Gd phase diagram [1998Zha] depicts the following line compounds, bFe17Gd2 (Ni17Th2-type hexagonal), aFe17 Gd2 (Zn17Th2-type rhombohedral), Fe23Gd6 (D8a, Mn23Th6-type cubic), Fe3Gd (Ni3Pu-type rhombohedral) and Fe2Gd (C15, MgCu2-type cubic). In the Fe-Sn system, the intermediate phases are: Fe5Sn3 (B82, Ni2In-type hexagonal), Fe3Sn2 (rhombohedral), FeSn (B35, CoSn-type hexagonal) and FeSn2 (C16, CuAl2-type tetragonal). The Gd-Sn system [1995Oka] has a number of intermediate compounds of fixed stoichiometry: Gd3Sn, Gd5Sn3, Gd5Sn4, Gd8Sn7, Gd11Sn10, Gd3Sn4, GdSn2, Gd3Sn7 and GdSn3. See [1995Oka] for a listing of the known structural details.

Ternary Phases Two ternary phases are known in this system. GdFexSn2 (x ~ 0.14)0.17) is ZrSi2-type orthorhombic phase based on the binary compound GdSn2. The increase in the cell volume with increase in the Fe content indicates that GdFex Sn2 is an insertion-type solid solution. The lattice parameters of GdFe0.14Sn2 are: a = 0.44444 nm, b = 1.6445 nm and c = 0.43672 nm [2004Mud]. The other ternary phase GdFe6 Sn6 is a true ternary compound. It has hexagonal lattice parameters a = 0.5369 nm and c = 0.4463 nm with YCo6Ge6 as the prototype. In the TbFe6Sn6-type orthorhombic setting, it has parameters a = 0.8927 nm, b = 1.870 nm and c = 0.5357 nm [2004Mud].

Isothermal Section With starting metals of 99.9 wt.% Fe, 99.8 wt.% Gd, and 99.99 wt.% Sn, [2004Mud] arc-melted alloy samples under

Fig. 1 Fe-Gd-Sn composite isothermal section at 597 and 397
C [2004Mud]

Journal of Phase Equilibria and Diffusion Vol. 28 No. 4 2007

387

Section II: Phase Diagram Evaluations Ar atm. The samples were annealed for 1 month at 597
C for Sn 55 at.%. The phase equilibria were studied mainly with x-ray diffraction. The composite isothermal section constructed by [2004Mud] is shown in Fig. 1. The binary Gd-Sn compounds Gd3Sn, Gd8 Sn7 and Gd3Sn4 were not found by [2004Mud].

1998Zha: W. Zhang, C. Li, X. Su, and K. Han, An Updated Evaluation of the Fe-Gd (Iron-Gadolinium) System, J. Phase Equilb., 1998, 19(1), p 56-63 2004Mud: Ya. Mudryk, L. Romaka, Yu. Stadnyk, O. Bodak, and D. Fruchart, X-ray Investigation of the R-Fe-Sn Ternary Systems (R-Y, Gd), J. Alloys Compd., 2004, 383, p 162-165

References 1995Oka: H. Okamoto, Comment on Gd-Sn (Gadolinium-Tin), J. Phase Equilib., 1995, 16(1), p 100-101

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Journal of Phase Equilibria and Diffusion Vol. 28 No. 4 2007