The system Hf–Ga–Sn at 600ºC and the crystal structure of Hf₅Ga_1.24-0.52Sn_1.76-2.48

Chem. Met. Alloys 4 (2011) 175-187

https://doi.org/10.30970/cma4.0200

Iryna VOZNYAK, Yaroslav TOKAYCHUK, Roman GLADYSHEVSKII

The isothermal section at 600ºC of the phase diagram of the ternary system Hf–Ga–Sn was constructed in the whole concentration range using X-ray diffraction and energy dispersive X-ray analysis. The binary gallides HfGa (structure type ThIn) and Hf₅Ga₃ (Mn₅Si₃) dissolve up to 17 at.% Sn, forming solid solutions characterized by constant Hf concentration. Based on the binary stannide Hf₅Sn₃ (Mn₅Si₃) an interstitial solid solution up to 11.1 at.% Ga is formed. Other binary compounds of the systems Hf–Ga and Hf–Sn do not dissolve noticeable amounts of the third component. One ternary compound, Hf₅Ga_1.24-0.52Sn_1.76-2.48, with homogeneity range 9 at.% Ga (Sn) is formed. Its crystal structure belongs to the structure type Nb₅SiSn₂ (Pearson symbol tI32, space group I4/mcm), which is a ternary variant of W₅Si₃. With increasing Sn content the unit-cell parameters within the homogeneity range increase from a = 10.9154(8), c = 5.51311(15) Å to a = 11.0203(7), c = 5.56591(16) Å. The structure is built up of two kinds of isolated column: face-sharing square antiprisms GaHf₈ and edge-sharing tetrahedra HfSn₄.

Projection of the structure of Hf₅Ga_1.24-0.52Sn_1.76-2.48 along [001]

Keywords

Hafnium / Gallium / Tin / Phase diagram / X-ray diffraction / Crystal structure / Solid solution