Crystal structure of the ternary compound γ-Al3FeSi

Abstract Ternary iron silicide aluminide γ -Al 3 FeSi crystals were grown from two Al—Fe—Si melts quenched in cold water. The crystal structures were determined from single-crystal X-ray data: trigonal symmetry, space group R -3 (n°148), unit cell parameters a = 10.2223(2) Å, c = 19.6791(4) Å ( V = 1781 Å 3 ) for the Si-poorer crystal and a = 10.1987(2) Å, c = 19.5320(3) Å ( V = 1759 Å 3 ) for the Si-richer one. The structure of γ -Al 3 FeSi may be described in terms of Al-cubes connected together by Al—Al pairs. The structure contains also Al cuboctaedra with one Fe—Al mixed atom in the center. The average chemical formula obtained from the refinements is Al 3 FeSi. This phase shows a partial disorder on the aluminium network because of the substitution of aluminum atoms by silicon. This substitution mechanism is at the origin of the large homogeneity range of this phase.