DEFECT CHEMISTRY OF CU2-YO AT ELEVATED-TEMPERATURES .2. ELECTRICAL-CONDUCTIVITY, THERMOELECTRIC-POWER AND CHARGED POINT-DEFECTS

The electrical conductivity and the Seebeck coefficient of Cu2O 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 (greater than or equal to 1200 K) and low oxygen partial pressure (less than or equal to 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 less than or equal to T less than or equal to 1250 K. The hole mobility is 3 less than or equal to nu(h) less than or equal to 6 cm(2)/Vs, and it decreases when the temperature increases. The electron mobility is higher than that of holes, with values of 150 less than or equal to nu(e) less than or equal to 200 cm(2)/Vs. The variation of the Fermi level within the Cu2O phase as a function of oxygen partial pressure and temperature was also determined.