Fe-Ga-Ho (Iron-Gallium-Holmium)

Abstract

[1987Lap] determined an isothermal section for this systetragonal symmetry. HoGa2.9-2.8Fe0.1-0.2 (t4) has the AuCu3type cubic structure. HoGa0.64-1.20Fe2.36-1.80 (t5) has the CeNi3tem at 597 8C, which depicts eight ternary compounds. type hexagonal structure. t6, t7, and t8 all lie on the line of constant Ho of 33.3 at.%. t6 has hexagonal symmetry. t7 has Binary Systems CeCu2 as the prototype. t8 is a Laves phase of the MgZn2-type. Table 1 lists the structural data of these compounds [1987Lap]. The Fe-Ga phase diagram was reviewed by [1990Oka]. The solid solution based on fcc Fe is restricted by a g loop. Isothermal Section Three ordered forms of the bcc solid solution, a, are known. a1 has the CsCl-type ordered structure; a2 is an unknown With starting metals of purity of 99.9% Fe, 99.99% Ga, type. The third ordered form, denoted here Fe3+xGa, has the and 99.86% Ho, [1987Lap] melted 140 alloy compositions BiF3-type structure. There are four other intermediate phases in an electric arc furnace under Ar atm. The alloys were in the system: Fe3Ga, Fe6Ga5, Fe3Ga4, and FeGa3; each of the annealed at 597 8C for 200 h and water quenched. The phase first two has two allotropic modifications. The Fe-Ho phase equilibria were mainly studied by x-ray powder diffraction. diagram has been reviewed by [1982Kub] and shows four line [1987Lap]’s ternary isothermal section at 597 8C is redrawn compounds: Fe17Ho2, Fe23Ho6, Fe3Ho, and Fe2Ho. The Gain Fig. 1 to agree with the accepted binary data. All the eight Ho phase diagram, as reviewed by [Massalski2], shows six ternary compounds listed in Table 1 are present at 597 8C. intermediate phases: Ga6Ho (stable below 312 8C), Ga3Ho, The binary compounds Fe17Ho2, Fe3Ho, and Fe2Ho dissolve Ga2Ho, Ga5Ho3, GaHo, and Ga3Ho5. In addition, [1987Lap] approximately 17, 11, and 22 at.% Ga, respectively, at conreported a compound at the composition: Ga2Ho3. [Pearson3] stant Ho content. The solubility of Fe in Ga-Ho compounds provides structural data on the compounds of the above or Ho in Fe-Ga compounds is negligible [1987Lap]. binary systems. References