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

Abstract

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, Gd 5Ge 3, Gd 5Si 3, Gd 5Ge 4, Gd 5Si 4, GdGe, GdSi, Gd 2Ge 3 and Gd 2Si 3, and the ternary compound Gd 5(Ge 1− x Si x ) 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, Gd 5(Ge,Si) 3 formed between Gd 5Ge 3 and Gd 5Si 3 (Mn 5Si 3-type structure), and Gd 2(Ge,Si) 3 formed between Gd 2Ge 3 and Gd 2Si 3 (AlB 2-type structure), were found in this isothermal section. The maximum solid solubilities of Si in Gd 5Ge 4 and GdGe at 900 °C are 10.3 and 35.0 at.%, respectively, while those of Ge in Gd 5Si 4 and GdSi at 900 °C are 20.5 and 11.5 at.%, respectively. The homogeneity range of Gd 5(Ge 1− x Si x ) 4 is from 13.3 to 22.0 at.% Si (or x from 0.3 to 0.495).