Phase transitions in copper chalcogenides II. The tellurides Cu3‐x Te₂ and CuTe

The thermal behaviour of the phases Cu 3‐x Te 2 and CuTe has been investigated by X‐ray diffraction at continuously varying temperature and by differential thermal analysis. Cu 3‐x Te 2 has an orthorhombic structure at room temperature which is closely related to the tetragonal structure of defective Cu 2 Sb type stable above 140°. Above 360° a face‐centred cubic form was found; the transition tetragonal ⇄ f.c.c. takes place via another (rhombohedral?) form. The atomic arrangements in the orthorhombic and f.c.c. forms have been studied. CuTe was found to disproportionate at 340° into Cu 3‐x Te 2 and a tellurium‐rich melt.