EFFECTS OF TEMPERATURE AND MICROSTRUCTURE ON THE ELASTIC PROPERTIES OF SELECTED Eu2O3-HfO2 COMPOSITIONS

摘要

Europium oxide is presently being tested for use as the control material in future nuclear power reactors. Elastic properties of europia and selected europia-rich compositions of the europia-hafnia system were investigated in this study. The sonic technique was employed to measure elastic moduli from room temperature to 1500°C.nSintered monoclinic europia specimens were found to have uncommonly low room temperature moduli values and to exhibit hysteresis between heating and cooling curves because of the presence of microcracks caused by thermal expansion anisotropy. Fine grained hot pressed europia as well as sintered speci¬mens that contained at least 6 mole % hafnia did not exhibit these characteristics. Photomicrographs revealed that grain growth suppression was produced by and related to the amount of hafnia introduced. Hysteresis loops in the moduli versus temperature measurements were exhibited only by those speci¬mens for which the average grain size was in excess of a critical value of 8 um.nDilatometer measurements indicated that thermal expansion was relatively constant over the compositional range of inter¬est.