ELECTRICAL-CONDUCTIVITY MEASUREMENTS ON CUPROUS BROMIDE, CUBR, IN THE PRESENCE OF OXYGEN

The influence of oxygen on the electrical conductivity of CuBr at 420-degrees-C was examined over an extended range of oxygen partial pressures (10(-20) < P(O2) < 10(-3) atm). While no effect was observed on the total conductivity, known to be predominantly ionic, an effect of oxygen could be detected in measurements of current in cells of the type ( - )Cu /CuBr/ C( + ), for P(O2) > 10(-17) atm. These observations are interpreted as being due to oxygen dissolution on the Br sublattice to form acceptors O(Br)' which compensate the relatively low electron density, n, formed as a consequence of nonstoichiometry, CuBr1-delta. The findings of n-type semi-conductivity is contrary to previous interpretations of polarization measurements on CuBr. The discrepancy can be explained on the basis of a decomposition reaction occurring at the graphite electrode, which was overlooked beforehand. Further, while a layer of Cu2O was observed to form at the Cu/CuBr interface, this was shown not to be the cause of the current dependence on P(O2) in the cell described above.