Solid-state electrochemical methods were used to investigate non-stoichiometric Cu2-xO at temperatures of between 873 and 1245K, under O partial pressures which ranged from 10-13 to 0.1atm. The point defects which were predicted to be predominant at high O partial pressures were neutral Cu vacancies, VCux. At low partial pressures, the predominant defects were predicted to be neutral Cu interstitials, Cuix, at temperatures of between 873 and 1245K, and VOx at temperatures above 1245K. The enthalpy of formation of VCux varied from 60.2kJ/mol at 1200K to 37.6kJ/mol at 950K. By using an average value of 43.1kJ/mol, it was deduced that the entropy of formation of VCux was equal to -5.5J/molK. The enthalpy of formation of Cuix was independent of temperature; with a value of 186kJ/mol. The entropy of formation of Cuix was 64.8J/molK.

Defect Chemistry of Cu2-yO at Elevated Temperatures. Part I: Non-Stoichiometry, Phase Width and Dominant Point Defects. O.Porat, I.Riess: Solid State Ionics, 1994, 74[3-4], 229-38