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hase Diagram Evaluations: Section II

Er-Fe-Sb (Erbium-Iron-Antimony) V. Raghavan

Recently, two isothermal sections were reported for this ternary system: one at 897 °C by [2004Mor] and the other at 500 °C by [2006Cai].

Binary Systems The Er-Fe phase diagram [Massalski2] shows four line compounds: Fe17Er2 (Ni17Th2-type hexagonal), Fe23Er6 (D8a, Mn23Th6-type cubic), Fe3Er (rhombohedral), and Fe2Er (C15, MgCu2-type cubic). Two intermediate phases are known in the Er-Sb system: Er5Sb3 (Y5Bi3-type orthorhombic [2004Mor]) and ErSb (B1, NaCl-type cubic). The Fe-Sb phase diagram [1997Ric] has two intermediate phases: FeSb1-x (41-49 at.% Sb; B81, NiAs-type hexagonal) and FeSb2 (C18, marcasite-type orthorhombic).

Ternary Isothermal Sections With starting metals of 99.8% Er, 99.9% Fe, and 99.99% Sb, [2004Mor ] arc-melted 8 ternary alloys under Ar atm. The samples were annealed at 897 °C (1170 K) for 2 weeks and quenched in water. The phase equilibria were studied with x-ray powder diffraction, local composition analysis, and metallography. The isothermal section at 897 °C (1170 K) constructed by [2004Mor ] is shown in Fig. 1. A ternary compound Er6FeSb2 (Zr6CoAs2-type hexagonal, denoted s here) is present. There is no measurable solubility of the third component in the binary compounds. With starting metals of 99.9% Er, 99.9% Fe, and 99.95% Sb, [2006Cai] arc-melted under Ar atm 12 binary and 11 ternary alloy samples. The final anneal was at 500 °C for 1 week, followed by quenching in liquid

Fig. 1 Er-Fe-Sb isothermal section at 897 °C (1170 K) [2004Mor]. Narrow two-phase regions are omitted

Journal of Phase Equilibria and Diffusion Vol. 29 No. 5 2008

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Section II: Phase Diagram Evaluations

Fig. 2 Er-Fe-Sb isothermal section at 500 °C [2006Cai]. Narrow two-phase regions are omitted

nitrogen. The phase equilibria were studied with metallography and x-ray powder diffraction. The isothermal section at 500 °C constructed by [2006Cai] is shown in Fig. 2. It is similar to the one at 897 °C (Fig. 1), except for the solidification of the Sb-rich liquid and the presence of FeSb2. The ternary compound Er6FeSb2 (s) is present. The solubility of the third component in the binary compounds is negligible.

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References 1997Ric: K.W. Richter and H. Ipser, Reinvestigation of the Binary Fe-Sb Phase Diagram, J. Alloys Compd., 1997, 247, p 247-249 2004Mor: A.V. Morozkin, Er-Fe-Sb System at 1170 K, J. Alloys Compd., 2004, 373, p L3-L4 2006Cai: G. Cai, X. Wei, and L. Zeng, The Isothermal Section of the Er-Fe-Sb Ternary System at 773 K, J. Alloys Compd., 2006, 420, p 133-135

Journal of Phase Equilibria and Diffusion Vol. 29 No. 5 2008