Defect chemistry of Cu 2−yO at elevated temperatures. Part I: Non-stoichiometry, phase width and dominant point defects

Abstract

The deviation from stoichiometry in Cu 2− y O was measured as a function of oxygen partial pressure, 10 −13≤ P O2≤0.1 atm, and temperature, 873≤ T≤1245 K, using a solid state electrochemical method. The measurements covered the whole width of the phase Cu 2− y O for the temperature range 873≤ T≤1245 K. The y− P O2− T relations are analyzed in order to identify the dominant point defects. It is found that in the high P O2 range of the phase, the dominant defects are neutral copper vacancies, V x Cu. In the low P O2 range there are two types of defects, dominating at different temperatures. At low temperatures the dominant defects are neutral copper interstitials, Cu x i. The analysis indicates that at temperatures higher than 1245 K the dominant defects are oxygen vacancies, V x O. The enthalpy and entropy for the formation of V Cu x and Cu i x are also determined.