Defect chemistry of Cu 2− yO at elevated temperatures. Part II: Electrical conductivity, thermoelectric power and charged point defects

Abstract

The electrical conductivity and the Seebeck coefficient of Cu 2O were measured as a function of temperature and oxygen partial pressure. The measurements were performed between 900 K and 1300 K and between 10 −12 atm and 0.15 atm. The results indicate that the dominant electronic charge carriers are holes, although at high temperatures (⩾ 1200 K) and low oxygen partial pressure (⩽ 10 −5 atm) there is also a significant contribution of electrons to the electrical conductivity and Seebeck coefficient. The dominant ionic point defects are doubly charged oxygen interstitials O″ i, dominating at temperatures above 1150 K, and singly charged copper vacancies V′ cu, dominating at temperatures below 950 K. The values of the enthalpy and entropy for the formation of the charged defects were found. The mobility values of holes and electrons were determined in the temperature range of 1000 K ⩽ T ⩽ 1250 K. The hole mobility is 3 ⩽, v h ⩽ 6 cm 2/Vs, and it decreases when the temperature increases. The electron mobility is higher than that of holes, with values of 150 ⩽ v e ⩽ 200 cm 2/Vs. The variation of the Fermi level within the Cu 2O phase as a function of oxygen partial pressure and temperature was also determined.