The phase relations in the Gd–Fe–Ga ternary system at 500 °C

Abstract

The isothermal section (500 °C) of the phase diagram of the Gd–Fe–Ga ternary system was investigated by X-ray powder diffraction analysis. Eleven binary compounds, GdGa 2, GdGa, Gd 3Ga 2, Gd 5Ga 3, GdFe 2, GdFe 3, Gd 2Fe 17, Fe 3Ga, Fe 6Ga 5, Fe 3Ga 4 and FeGa 3, have been confirmed. Two ternary compounds, GdFe 5.3Ga 6.7 and GdFe 5Ga 7, were found in this ternary system at 500 °C. The compound GdFe 5.3Ga 6.7 is orthorhombic ScFe 6Ga 6-type structure (space group Immm) with a = 0.8567 (9), b = 0.86960 (9) and c = 0.50782 (5) nm, while the compound GdFe 5Ga 7 is tetragonal ThMn 12-type structure (space group I4/ mmm) with a = 0.8651(1) and c = 0.50934 (6) nm. The isothermal section at 500 °C consists of 16 single-phase regions, 31 two-phase regions and 16 three-phase regions. The maximum solid solubilities of Ga in GdFe 2, GdFe 3, Gd 2Fe 17 are 9.2, 9.0, and 44.3 at.% respectively. The homogeneity range of GdGa 2 is from 22 to 33.3 at.% Ga in Gd–Ga side but the solid solubility of Fe in this compound is very small. The homogeneity range of GdFe 5Ga 7 is from 53.8 to 59.2 at.% Ga. Very limited solid solutions were measured in the other compounds.