Phase transitions in the Cu₂S nanowires

Phase transitions in the Cu₂S nanowires have been studied as a function of temperature and pressure. Differential scanning calorimetry (DSC) shows an endothermic process at 101.8 °C upon heating, corresponding to the phase transition from γ-Cu₂S (monoclinic) to β-Cu₂S (hexagonal) in the bulk (103.5 °C). However, the reverse phase transition was found to be much lower (74.8 °C). X-ray diffraction (XRD) demonstrates that the c-axis of γ-Cu₂S is transformed to the c-axis of β-Cu₂S owing to the positional disorder of the Cu atoms. Two high-pressure phases of Cu₂S have been identified using a diamond anvil cell and the energy-dispersive XRD technique.