Crystal structure determination of a ternary Cu(In,Sn)₂ intermetallic phase by electron diffraction

Small grains of an intermetallic phase with an approximate composition Cu(In,Sn)₂ were observed in a metal matrix composite obtained from powders of a Cu-Al-Ni shape-memory alloy and an In-Sn matrix alloy. Samples of this composite were prepared for transmission electron microscopy and the crystal structure of the intermetallic phase was carefully investigated by applying electron diffraction techniques (microdiffraction, convergent-beam electron diffraction and precession), based on the analysis of the symmetry and the relative positions of reflections in the zero- and high-order Laue zones. It was found that the intermetallic phase has a body-centred tetragonal unit cell with lattice parameters a = 0.70 (3) nm and c = 0.56 (2) nm. Its crystal symmetry can be described by the I4/mcm (No. 140) space group.