Pure uo2 sinters readily at temperatures below 1600°c when non-stoichiometric oxygen introduced during the presintering treatment is available for diffusion and subsequent densification. In the absence of excess oxygen sintering occurs at temperatures above 1600°C by self-diffusion of stoichiometric oxygen in uo2 • Grain growth occurs when open porosity has been eliminated and is controlled by the diffusion rate of closed pores in uo2.
Watson, James Frederick and Wilder, D. R., "Roles of niobium pentoxide, vanadium pentoxide and titanium dioxide in the grain growth and sintering of uranium dioxide" (1960). Ames Laboratory Technical Reports. 36.