Cu-deficiency induced structural transition of Cu2−xTe

All the reported structures of Cu₂Te are found to be metastable with respect to the phase separation Cu₂Te → Cu2−xTe + xCu, which causes a structural transition of Cu2−xTe from the monoclinic structure (stable when x = 0) to the trigonal structure (0.125 ≤ x ≤ 0.625). The experimental XRD peaks of Cu2−xTe samples should be attributed to the trigonal structure.