The effect of gadolinium content on the thermal conductivity of near-stoichiometric (U,Gd)O2 solid solutions

The thermal conductivities of near-stoichiometric (U, Gd)O2 solid solutions containing CdOsub(1.5) up to 15 mol% were determined in the temperature range 700 to 2000 K from thermal diffusivities measured by the laser flash method. Temperature dependence of the thermal conductivities up to around 1600 K could be expressed by the phonon conduction equation K = (A + BT)-1. The thermal conductivity decreased gradually with an increase of gadolinium content. Thermal resistivities caused by lattice defects were calculated from a theoretical model considering U4+, U5+ and Gd3+ ions as phonon scattering centers. It was found that this model was in good agreement with the experimental results. The calculation based on this model indicates that the lattice strain effect on the lattice defect thermal resistivity is much larger than the mass effect. (orig.)