THE DIELECTRIC-CONSTANT OF UO2 BELOW THE NEEL POINT

The authors report measurements of the frequency-dependent dielectric constant from 4. 2 K to above the phase transition at 30 K. The static dielectric constant of 23. 6 at 4. 2 K is comparable with accepted values at higher temperatures; it is essentially identical in both phases. The effects of undergoing the transition on the dielectric constant are marginal (about 1%) and take place in the temperature range 29 K to 37 K. The displacement of the oxygen sublattice, which occurs at the Neel point, should produce only a 0. 05% change in the dielectric constant and of the opposite sense to that measured. Hence structural changes at the transition are not the primary source of the observed small difference between the dielectric constant in the two phases which probably accrues from the influence of the displacement on a defect-related contribution.