Heat capacity measurement of U1−yLayO2 (y=0.044, 0.090, 0.142) from 300 to 1500 K

T. Matsui; Y. Arita; K. Naito

doi:10.1007/bf02117557

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Journal of Radioanalytical and Nuclear Chemistry

Volume/Issue:: Volume 143: Issue 1

Heat capacity measurement of U_1−yLa_yO₂ (y=0.044, 0.090, 0.142) from 300 to 1500 K

Authors:

T. Matsui

T. Matsui Nagoya University Department of Nuclear Engineering, Faculty of Engineering Furo-cho, Chikusa-ku 464-01 Nagoya (Japan)

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Y. Arita

Y. Arita Nagoya University Department of Nuclear Engineering, Faculty of Engineering Furo-cho, Chikusa-ku 464-01 Nagoya (Japan)

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K. Naito

K. Naito Nagoya University Department of Nuclear Engineering, Faculty of Engineering Furo-cho, Chikusa-ku 464-01 Nagoya (Japan)

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Pages:: 149–156

Online Publication Date:: 14 Sep 2005

Publication Date:: 17 Nov 1990

Article Category:: Research Article

DOI:: https://doi.org/10.1007/bf02117557

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Abstract

Heat capacities of U_1–yLa_yO₂ were measured by means of direct heating pulse calorimetry in the temperature range from 300 to 1500 K. An anomalous increase in the heat capacity curve of each sample was observed similarly to the case of U_1–yGd_yO₂, found recently in our laboratory. As the lanthanum content of U_1–yLa_yO₂ increased, the onset temperature of an anomalous increase in the heat capacity decreased and the excess heat capacity increased. The enthalpy of activation (H_f) and the entropy of activation (S_f) of the thermally excited process, which cause the excess heat capacity were obtained to be 2.14, 1.63 and 1.50 eV and 39.4, 34.2 and 31.8 J·K^–1·mol^–1 for U_0.956La_0.044O₂, U_0.910La_0.090O₂ and U_0.858La_0.142O₂, respectively. The values at zero La content extrapolated by using the data of H_f and S_f for U_1–yLa_yO₂ were in good agreement with the experimental values of undoped UO₂ so far reported, similarly to the case of Gddoped UO₂. The electrical conductivities of U_1–yLa_yO₂ (y=0.044 and 0.142) were also measured as a function temperature. No anomaly was seen in the electrical conductivity curve. It may be concluded that the excess heat capacity originates from the predominant contribution of the formation of oxygen clusters and from the small contribution of the formation of electron-hole pairs.

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Journal of Radioanalytical and Nuclear Chemistry

Print ISSN:: 0236-5731

Online ISSN:: 1588-2780

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Journal of Radionalytical and Nuclear Chemistry
Language	English
Size	A4
Year of Foundation	1968
Volumes per Year	1
Issues per Year	12
Founder	Akadémiai Kiadó
Founder's Address	H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher	Akadémiai Kiadó Springer Nature Switzerland AG
Publisher's Address	H-1117 Budapest, Hungary 1516 Budapest, PO Box 245. CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible Publisher	Chief Executive Officer, Akadémiai Kiadó
ISSN	0236-5731 (Print)
ISSN	1588-2780 (Online)