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 m easured as a function of temperature and oxygen partial pressure. The measurements were performed between 900 K and 1300 K and between 10(-1 2) atm and 0.15 atm. The results indicate that the dominant electronic charge carriers are holes, although at high temperatures (greater tha n or equal to 1200 K) and low oxygen partial pressure (less than or eq ual to 10(-5) atm) there is also a significant contribution of electro ns to the electrical conductivity and Seebeck coefficient. The dominan t ionic point defects are doubly charged oxygen interstitials O-i'', d ominating at temperatures above 1150 K, and singly charged copper vaca ncies V-cu', dominating at temperatures below 950 K. The values of the enthalpy and entropy for the formation of the charged defects were fo und. 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 equa l to 1250 K. The hole mobility is 3 less than or equal to nu(h) less t han or equal to 6 cm(2)/Vs, and it decreases when the temperature incr eases. 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.