Electrical Conductivity of Uranium Dioxide

Abstract

The electrical conductivity of nearly stoichiometric single‐crystal and polycrystalline uranium dioxide was measured from room temperature to 3000°K. Below approximately 550°K, the curve of log σ versus T−1 is linear with a calculated activation energy of approximately 0.17 ev. Between 550° and 1250°K, however, the shape of the curve changes; this change varies from one specimen to another. The electrical conductivity increases rapidly with increasing temperature above 1250°K with a change from p‐type to n‐type conduction. The best linear fit of the log σ versus T−1 curve above 1400°K is σ= 3.57 × 103e−(1.15 ev/KT). Above 1900°K, the curve deviates slightly from linearity and is best fit by the equation σ= 2.10 × 10−2T1.4e−(0.916 ev/KT).

Thermal variation of the optical absorption of UO2: determination of the small polaron self-energy

“…Among the different physical properties, the electrical and thermal properties have received special attention since they exhibit singular behaviour in the vicinity of 1300 K which is the typical temperature of UO 2 pellets in normal PWR operation. Around this range of temperature, it is observed, indeed, that electrical conductivity and heat capacity both present a drastic change in their temperature dependence [1][2][3][4][5][6][7]. This abnormal behaviour has been attributed either to the emergence of intrinsic electronic charge carriers [8,9], or to simultaneous electronic and oxygen anti-Frenkel pair disorder [10].…”

“…the electrical transition, has been modelled and, according to many authors [1,2,8,[13][14][15][16], is driven by the occurrence of electron-hole pairs, which are schematically represented by the following disproportionation reaction 2U 4þ (5f 2 ) () U 3þ (5f 3 ) + U 5þ (5f 1 ) [8,16,17]. The interpretation of such an electronic defect formation requires the knowledge of the electronic structure of UO 2 which has been determined only recently [18][19][20] because of the difficulty encountered with the modelling of 5f electrons.…”

Investigation of the skull melting method for the generation of particulate material of inorganic compounds

“…The molar heat capacity is given for a temperature range 298.15 K # T # 3210 K by: (5) and for 3120 # T # 4500 K by:…”

Oxygen diffusion in hypostoichiometric uranium dioxide

“…r = /T iHpexp^) exp(-^) (52) where aH,-= 35.6 kcal/mole aS-= 18.2 e.u. However, as Thorn et al [47] indicated, to use 5f orbitals as the valence band may be more plausible than 4f.…”