ELECTRICAL-CONDUCTIVITY AND DEFECT STRUCTURE OF CR2O3 .1. HIGH-TEMPERATURES (GREATER-THAN-SIMILAR-TO-1000-DEGREES-C)

The electrical conductivity of Cr2O3 has been studied by the four-point ac technique as a function of oxygen activity (O2 + Ar, CO + CO2 and H-2 + H2O mixtures) in the temperature range 440-1500-degrees-C. This paper focuses on the conductivity behaviour at high temperatures (> approximately 1000-degrees-C) and under these conditions it is concluded that the predominant defect structure situation involves the intrinsic electronic equilibrium. From the conductivity measurements it is estimated that the corresponding energy gap is 320 kJ/mol (3.3 eV). The results also suggest that hydrogen may dissolve in chromia in hydrogen-rich atmospheres at high temperatures but in amounts that do not significantly affect the electrical conductivity. The defect structure of chromia at high temperatures is discussed.