Thermal conductivity of (Pu1−xNdx)O2−y and (Pu1−xYx)O2−y solid solutions

The thermal conductivities of (Pu1−xRx)O2−y solid solutions (R = Nd and Y) containing RO1.5 up to 10 mol% were determined in the temperature range 700–1450 K from thermal diffusivities measured by the laser flash method. The thermal conductivities satisfied the phonon conduction equation K = (A + BT)−1 within ± 7%. The values of A, corresponding to the lattice defect thermal resistivity, increased linearly with the neodymium or yttrium content, while those of B were nearly constant. The increasing rate of A for (Pu, Nd)O2−y solid solutions was slightly larger than that for (Pu, Y)O2−y. These increases were reasonably explained by the lattice defect model in wich Pu4+, R3+, O2− ions, and oxygen vacancy in the solid solutions were considered as phonon scattering centers. For both solid solutions, the lattice strain effects on the lattice defect thermal resitivities were in preference to the mass effects. In addition, the stoichiometry effects on the additional defect thermal resistivities were about 1.3 times larger than the cation effects.