ELECTRICAL MEASUREMENTS ON CUBR

In an attempt to clarify the relative contributions of bulk and interfacial effects to the overall electrical conductivity of CuBr, four-probe van der Pauw-type measurements were performed over an extensive range of temperature, 165-488-degrees-C. While our conductivity results agree reasonably well with previously reported data in the low temperature range, T < 385-degrees-C, characteristic of the gamma phase, they are almost an order of magnitude higher for the beta phase (385-degrees-C < T < 469-degrees-C). The source of the discrepancy was traced to the irreversibility of the Cu-electrode in contact with the beta-phase. In contrast, the Cu-electrode was found to be reversible under low frequency ac excitation for the gamma phase. Under dc current conditions, however, the electrodes deteriorated even in the gamma phase after removal of approximately 1 mum of Cu from the electrode. The enthalpy of migration obtained from the new conductivity data is 0.35 eV for the beta phase and 1.1 eV for the gamma phase. The Frenkel pair formation enthalpy is neglegible in the beta phase, and 1.50 eV in the gamma phase.