Synthesis and thermal conductivity of Y6UO12

Y6UO12 was synthesized by solid-state reactions of Y2O3 and U3O8. The high-density pellet of Y6UO12 was prepared by the spark plasma sintering followed by heat treatment in air for oxygen supplementation. The thermal conductivity (κ) was evaluated using the laser flash method from room temperature to 1173 K. The κ of Y6UO12 decreased with increasing temperature in the whole temperature range, indicating that the phonon contribution was predominant. The room temperature κ value of Y6UO12 was 4.90 Wm-1K-1. The magnitude relationship of κ among Y6UO12, Y6WO12, and Yb6WO12, i.e. κ of Yb6WO12 < κ of Y6UO12 < κ of Y6WO12, was discussed based on the general lattice thermal conductivity theory. (author)