, Volume 39, Issue 5-6, pp 411-435

Oxidation of copper and electronic transport in copper oxides

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Abstract

Oxidation of copper and electronic transport in thermally-grown large-grain polycrystals of nonstoichiometric copper oxides were studied at elevated temperatures. Thermogravimetric copper oxidation was studied in air and oxygen at temperatures between 350 and 1000°C. From the temperature dependence of the oxidation rates, three different processes can be identified for the oxidation of copper: bulk diffusion, grain-boundary diffusion, and surface control with whisker growth; these occur at high, intermediate, and low temperatures, respectively. Electrical-conductivity measurements as a function of temperature (350–1134°C) and oxygen partial pressure (10−8–1.0 atm) indicate intrinsic electronic conduction in CuO over the entire range of conditions. Electronic behavior of nonstoichiometric Cu2O indicates that the charge defects are doubly-ionized oxygen interstitials and holes. The calculated enthalpy of formation of oxygen ( \(\Delta H_{{\text{O}}_{\text{2}} }\) ) and hole-conduction energy (EH) at constant composition for nonstoichiometric Cu2O are 2.0±0.2 eV and 0.82±0.02 eV, respectively.

This work was supported by the U.S. Department of Energy, under Contract W-31-109-Eng-38.