Factors governing microstructure development of Cr2O3-doped UO2 during sintering

Sintering and grain growth of compacted uranium dioxide powder pellets dope d with Cr2O3 were investigated at constant heating rates ranging from 75 to 500 K h(-1). The influence of parameters such as the oxygen potential of t he sintering atmosphere and pellet green density on the final microstructur e was studied. Dilatometric analysis and monitoring of microstructural deve lopment revealed a phenomenon of abnormal grain growth promoting densificat ion. The existence of a eutectic: between Cr and Cr2O3 is also discussed. G rain growth does not appear to be widely affected by small differences in r esidual porosity, which is a function of green density, so that it is possi ble to propose a solubility limit for Cr2O3 in stoichiometric: UO2 at 1700 degreesC. Examination of microstructural changes during annealing, with or without pore formers, showed the existence of limiting grain sizes for dope d samples above the solubility limit. Lastly, experimental sintering condit ions need to be checked in order to obtain reproducible results. (C) 2001 E lsevier Science B.V. All rights reserved.