Stacking faults in uranium dioxide

Abstract

Specimens of uranium dioxide have been quenched in an arc furnace from temperatures just below the melting point, cut into slices and chemically thinned for examination by transmission electron microscopy. Defects in the form of stacking faults and tetrahedra have been observed. Complete contrast experiments have been successfully carried out on some of these stacking faults and reveal a 1/6[1͞21] displacement vector lying in the fault plane. (Ill) and (201) stacking fault planes have been identified and it is thought that many more stacking fault planes exist having the displacement vector as zone axis. A combination of dark-field and bright-field microscopy shows that the faults are intrinsic. The tetrahedra are thought to be stacking faults lying on all four {111} planes and are attributed to dissociation of Frank sessile loops formed by vacancy condensation on {111} planes.