X-RAY DIFFRACTION FROM DEFORMED CERIUM: EFFECTS DUE TO EXTRINSIC STACKING FAULTS

Preliminary measurements of the peak shifts in the X-ray powder pattern of cerium cold-worked by filing at room temperature are reported. Because cerium oxidizes rapidly in the atmosphere, the experimental procedure is more complicated than that usually followed in the preparation of coldworked metal filings for the measurement of intrinsic faults. The preliminary data on coldworked cerium, although of lower accuracy than that normally attainable in this type of work, nevertheless showed peak displacements in the Debye-Scherrer pattern that were in most cases in the direction theoretically predicted for relatively low probabilities of extrinsic stacking faults. A more detailed investigation is required to verify the line broadening and asymmetry effects produced in the line profiles. The observations were complicated by an apparent annealing out of the peak shifts at room temperature although the increased (extrapolated) lattice parameter remained. (Author)