Determination of thermodynamics and kinetics of point defects in Cu2O using the Rosenburg method

The Rosenburg method has been applied to determine physicochemical properti es of Cu2O at 900-1000 degrees C and oxygen pressures from 0.005 to 0.1 atm . The defect concentration was proportional to p(O2)(1/4), whereas the defe ct diffusion coefficient was essentially independent of the ambient oxygen pressure. This is interpreted to reflect that the dominating defect in Cu2O is neutral Cu vacancies. The formation enthalpy of neutral copper vacancie s was observed to be approximately 60 kJ/mol and the formation entropy appr oximately -11 J/mol K. Migration enthalpies and entropies have been calcula ted from the temperature dependence of the defect diffusion data and are ap proximately 54 kJ/mol and 5.8 J/mol K, respectively. Combination of the ent halpy of formation and migration of the vacancies yields an enthalpy for Cu self-diffusion in Cu2O of approximately 115 kJ/mol. (C) 1999 The Electroch emical Society. S0013-4651(98)04-093-2. All rights reserved.