The electrical impedance of single-crystal urania at elevated temperatures

The electrical admittance of single-crystal urania has been measured from 300 to 1500 K, over a frequency range of 10 Hz to 10 MHz, using complex impedance spectroscopy. The data have been analyzed using a simple equivalent circuit of a parallel element comprising a conductance and a capacitance connected in series with a separate capacitance. The simple equivalent circuit also reanalyzes successfully the frequency dependence of the electrical conductivity found by Bates and his co-workers, giving results consistent with the present work. The conductance data show a distinct “kink” at about 1300 K, which is in good agreement with previous work, as are the activation energies: 0.12 eV (T < 1300 K) and 1.4 eV (T > 1300 K). Results are used to estimate the ambipolar contribution to the thermal conductivity above 1500 K.