Al-Fe-Ge: New ternary compounds and phase equilibria at 800 °C

The isothermal sections of Al-Fe-Ge at 800 °C and 780 °C were studied by a combination of SEM/EDX with X-ray powder diffraction. Two new ternary compounds were structurally characterised by means of single-crystal XRD measurements: Al3-xFeGe2+x, I4/mcm, a = 6.2303(11) Å, c = 9.710(2) Å, V = 376.9 ų, Z = 4, Rint = 0.031, wR2 = 0.038 and Al1+xFeGe1-x, Fddd, a = 8.627(2) Å, b = 4.9139(8) Å, c = 16.369(3) Å, V = 693.9 ų, Z = 16, Rint = 0.039, wR2 = 0.053, which crystallise in the Ga5Pd and CuMg2 structure types, respectively. Considerable solid solution ranges mainly based on Al/Ge substitution were found for all binary and ternary phases present in this section. An apparently incommensurate superstructure of Al5Fe2 is triggered by Ge-additions.