The frequency dependent response of the electrical impedance of UO2

AC impedance techniques in the frequency range 5 Hz to 5 MHz have been employed to measure dielectric properties of single crystal UO2 in the form of plate specimens. The dielectric constant has been measured down to 4 K, giving results consistent with previous reports. Both barrier and volume effects have been shown to contribute to the measured impedances. The barrier effects account for the anomalously large capacitances observed in previous attempts to measure the dielectric constant by the conventional plate technique. Activation energies for carriers in both boundary and bulk regions are similar (0.18 to 0.25 eV). The behaviour is consistent with the presence of electronic holes present in the concentrations to be expected from small deviations from stoichiometry.