RELAXATION PEAKS IN SINTERED UO2-U4O9 PELLETS

The internal friction of sintered pellets of compositions from UO2.00 to UO2.25, including the phases UO2+x and U4O9-y, was measured by an ultrasonic attenuation method over the temperature range from -196 to + 200 °C. Internal friction maxima were observed at about -145 and +85 °C, when measured at 5 Me/sec. The higher temperature maximum can be analyzed into two peaks, one of which increased with the amount of the U4O9-y phase. This one is associated with the phase transition in U4O9-y and the other is attributed to a reorientation of interstitial oxygen atoms in UO2+x. The height of the peak below room temperature was proportional to the amount of U4O9-y, phase. This peak may be due to electronic relaxation in the U4O9-y, phase, induced by dislocation motion. © 1969.