Lattice thermal expansion studies on single-phase compositions in CeO2-ThO2-ZrO2 system

Earlier we reported the phase relations in the CeO2-ThO2-ZrO2 system under slow cooled conditions from 1400 °C; ceria was used as a surrogate material for plutonia. A number of single-phase compositions with fluorite-type structure were identified in this pseudo-ternary system. For example, about 5 and 20 mol% of zirconia could be dissolved in the lattice of thoria and ceria, respectively. 10 mol% zirconia was incorporated in the lattice of Th0.5Ce0.5O2. The lattice thermal expansion behaviour of a number of single-phase compositions in the temperature range from 293 to 1473 K, as investigated by high temperature XRD, are reported. For example, the average lattice thermal expansion coefficient of pure thoria was found to be 9.58 × 10−6, which increased to 11.91 × 10−6 K−1 in the composition Th0.05Ce0.90Zr0.05O2.