Thermal expansion and self-irradiation damage in curium nitride lattice

A powder sample of curium nitride (CmN) containing 0.35%-Pu and 3.59%-Am as actinide impurities was prepared by carbothermic nitridation of the oxide. The lattice expansion induced by self-irradiation damage at room temperature was measured as a function of time. The saturated Δa/ao value was 0.43%, which is greater than those for transuranium dioxides available in literature. The undamaged lattice parameter at 297 ± 1 K was determined to be 0.50261 ± 0.00006 nm. Temperature dependence of the lattice parameter was measured by a high temperature X-ray diffractometer in the temperature range up to 1375 K. The linear thermal expansion from 293 to 1273 K was 0.964% and the corresponding thermal expansion coefficient was 9.84 × 10−6 K−1. Comparing with the other actinide nitrides, it was found that CmN lies between the higher expansion nitrides (PuN and AmN) and the lower expansion nitrides (UN and NpN).