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Phase Diagram Evaluations: Section II

Fe-Ho-Sb (Iron-Holmium-Antimony) V. Raghavan

An isothermal section was determined for this system at 500 °C by [2004Zen], which depicts a ternary compound FeHo4Sb.

Binary Systems In the Fe-Ho system [1982Kub], there are four intermediate phases: Th2Ni17-type hexagonal phase Fe17Ho2, Th6Mn23-type cubic phase Fe23Ho6, PuNi3-type rhombohedral phase Fe3Ho, and MgCu2-type cubic phase Fe2Ho. The Fe-Sb phase diagram [1993Oka] has two intermediate phases. The ␧ phase, with the NiAs-type hexagonal structure, has a homogeneity range of 40-47 at.% Sb. FeSb2 is a line compound with orthorhombic symmetry. The Ho-Sb phase diagram [1984Abd] depicts four line compounds: Ho5Sb3, Ho4Sb3, HoSb, and HoSb2. At 500 °C, Ho5Sb3 (Mn5Si3-type hexagonal), the low-temperature form of HoSb (NaCl-type cubic), and HoSb2 (orthorhombic) are present [1984Abd]. [2004Zen] did not find HoSb2 at 500 °C.

Ternary Isothermal Section Using starting metals of 99.5% Fe, 99.9% Ho, and 99.95% Sb, [2004Zen] arc melted or induction melted 122

alloy compositions under Ar atm. The samples were given a final anneal at 500 °C for 200 h and quenched into liquid nitrogen. The phase equilibria were studied by x-ray powder diffraction and scanning electron microscope with energy dispersive analytical attachment. The isothermal section constructed by [2004Zen] at 500 °C is redrawn in Fig. 1. The binary phases show little solubility for the third component. A ternary compound FeHo4Sb of fixed stoichiometry is present. It has hexagonal symmetry with a ⳱ 0.8126 nm and c ⳱ 0.4142 nm [2004Zen].

References 1982Kub: O. Kubaschewski, Iron-Holmium, Iron—Binary Phase Diagrams, Springer-Verlag, Berlin, Germany, 1982, p 111-112 1984Abd: M.N. Abdusaljamove, O.R. Burnashev, and K.E. Mironov, The Ho-Sb Alloy System, J. Less-Common Met., Vol 102, 1984, p L19-L22 1993Oka: H. Okamoto, Fe-Ho (Iron-Holmium), Phase Diagrams of Binary Iron Alloys, H. Okamoto, Ed., ASM International, 1993, p 179-181 2004Zen: L. Zeng and H. Zhao, The 773 K Isothermal Section of the Ho-Fe-Sb Ternary System, J. Alloys Compd., Vol 366, 2004, p 201-204

Fig. 1 Fe-Ho-Sb isothermal section at 500 °C [2004Zen]

Journal of Phase Equilibria and Diffusion Vol. 25 No. 6 2004

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