Isothermal section of the Gd–Ge–Si ternary system at 900 °C

Phase equilibria in the Gd-rich Gd–Ge–Si ternary system (Gd ≥ 40 at.%) at 900 °C were investigated mainly by X-ray powder diffraction. The binary compounds, Gd5Ge3, Gd5Si3, Gd5Ge4, Gd5Si4, GdGe, GdSi, Gd2Ge3 and Gd2Si3, and the ternary compound Gd5(Ge1−xSix)4 have been confirmed. The isothermal section of this system at 900 °C was constructed. It is composed of 8 single-phase regions, 10 two-phase regions and 6 three-phase regions. Two ternary solid solutions, Gd5(Ge,Si)3 formed between Gd5Ge3 and Gd5Si3 (Mn5Si3-type structure), and Gd2(Ge,Si)3 formed between Gd2Ge3 and Gd2Si3 (AlB2-type structure), were found in this isothermal section. The maximum solid solubilities of Si in Gd5Ge4 and GdGe at 900 °C are 10.3 and 35.0 at.%, respectively, while those of Ge in Gd5Si4 and GdSi at 900 °C are 20.5 and 11.5 at.%, respectively. The homogeneity range of Gd5(Ge1−xSix)4 is from 13.3 to 22.0 at.% Si (or x from 0.3 to 0.495).