Effect of step wise variation of oxygen potential during the isothermal sintering on the grain growth behavior in Cr2O3 doped UO2 pellets

To study the effect of oxygen partial pressure on grain growth in Cr2O3 doped UO2 pellets, small amount of Cr2O3 doped UO2 samples have been sintered with and without a stepwise change of sintering atmospheres. An introduction of a stepwise increase of oxygen potential during the isothermal sintering stage enhances the grain growth of UO2 pellets greatly. This stepwise sintering effect has been explained in terms of a maximized residual Cr3+ concentration in grain boundaries throughout the entire sintering process. It was demonstrated that a stepwise sintering technique can reduce the doped amount of Cr2O3 to a minimum level while keeping the large grain size.