Preparation of morphology controlled Th1 − xUxO2 sintered pellets from low-temperature precursors

Dense sintered samples of Th1 − xUxO2 solid solutions were prepared from the initial precipitation of oxalate precursors through two different wet chemical routes, based either on the direct precipitation of the cations or on the use of hydrothermal method. For both low-temperature precursors, the specific surface area was followed versus the heating temperature and the influence of the conversion step on the oxide powder reactivity was evidenced since it allowed to obtain reactive surfaces in the range of 15–45 m2 g−1 without any additional grinding step. From dilatometric studies, the operating conditions required for the complete densification of the Th1 − xUxO2 pellets were set to a heat treatment of 3 h at 1500 °C. In these conditions, the density of the samples lies between 94% and 99% of the calculated value whatever the preparation method chosen which appeared very promising compared to the results already reported under inert atmosphere. The initial precipitation of low-temperature precursors thus allowed to lower the sintering temperature by about 100 °C while the use of hydrothermal conditions significantly improved the cationic distribution in the sintered samples, as shown from EPMA statistical experiments.

Graphical AbstractSintered Th1 − xUxO2 pellets were prepared from the precipitation of oxalate precursors. The influence of the conversion step on the powder reactivity was evidenced then the operating conditions leading to the densification were determined. After 3 h at 1500 °C, the density reached up to 99%, showing that the use of precursors lowered the sintering temperature while it improved the cationic homogeneity.Figure optionsDownload as PowerPoint slide