Heat capacity measurement and EXAFS study of (U0.85Mg0.15)O2?x
forx=0 and 0.11 |
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| Authors: | Y Arita T Matsui H Ohno K Kobayashi |
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| Affiliation: | (1) Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, 464-01 Nagoya, Japan;(2) Office of Synchrotron Radiation Facility Project, Japan Atomic Energy Research Institute, Tokai, 319-11 Ibaraki, Japan;(3) Photon Factory, National Laboratory for High Energy Physics, Tsukuba, 305 Ibaraki, Japan |
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| Abstract: | Heat capacities and electrical conductivities of (U0.85Mg0.15)O2−x
(x=0 and 0.1) were measured simultaneously by means of a direct heating pulse calorimeter (DHPC) in the temperature range from
300 to 1500 K. Anomalous increases in the heat capacity curves of (U0.85Mg0.15)O2−x) (x=0 and 0.1) were observed above about 800 and 1150 K, respectively. The values for the enthalpy of oxygen Frenkel defect formation
were calculated from the excess heat capacity and were found to be similar to those for UO2 doped with rare earth elements. On the other hand, no anomaly was seen in the electrical conductivity curve around the onset
temperature of the anomalous increase in the heat capacity. It was, therefore, concluded that the excess heat capacity originates
from the predominant contribution of the formation of Frenkel pair-like defects of oxygen. An extended X-ray absorption fine
structure (EXAFS) experiment shows a different environment of oxygen around uranium and magnesium, and this should be a cause
of the onset temperature difference.
Paper presented at the Fourth Asian Thermophysical Properties Conference, September 5, 8, 1995, Tokyo, Japan. |
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| Keywords: | EXAFS study Frenkel defects of oxygen heat capacity heat capacity anomaly Mg-doped UO2 |
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