The isothermal section (500 °C) of the phase diagram of the ternary system GeHoSi

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The isothermal section (500 °C) of the phase diagram of the ternary system GeHoSi (40 at.% Ho or less) was investigated by X-ray diffraction, differential thermal microanalysis, optical microscopy and electron-probe microanalysis techniques. The isothermal section consists of seven single-phase regions, ten two-phase regions and four three-phase regions. The single-phase regions in this isothermal section correspond to the binary compounds in the binary systems HoGe or HoSi. No new ternary compound was found in this isothermal section. The β phase is a non-variable compound while the α phase is the continuous series of solid solutions of germanium and silicon with a small quantity of holmium. The other five single-phase regions are all limited solid solutions of silicon in (Ge, Ho) or germanium in (Ho, Si) binary compounds with the holmium being nearly invariant. The θ phase (HoGe 1.56) is a tetragonal system with a = 4.051 A ̊ , c = 13.651 A ̊ and corresponds to the compound HoGe 1.7 reported previously.