caa a22 4500 465732577 CHVBK 20180323111745.0 cr unu---uuuuu 170327e19901101xx s 000 0 eng 10.1007/BF02117557 doi (NATIONALLICENCE)springer-10.1007/BF02117557 Heat capacity measurement of U1−yLayO2 (y=0.044, 0.090, 0.142) from 300 to 1500 K [Elektronische Daten] [T. Matsui, Y. Arita, K. Naito] Heat capacities of U1−yLayO2 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 U1−yGdyO2, found recently in our laboratory. As the lanthanum content of U1−yLayO2 increased, the onset temperature of an anomalous increase in the heat capacity decreased and the excess heat capacity increased. The enthalpy of activation (ΔHf) and the entropy of activation (ΔSf) 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 U0.956La0.044O2, U0.910La0.090O2 and U0.858La0.142O2, respectively. The values at zero La content extrapolated by using the data of ΔHf and ΔSf for U1−yLayO2 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 U1−yLayO2 (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. Akadémiai Kiadó, 1990 Matsui T. Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-01, Nagoya, (Japan) aut Arita Y. Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-01, Nagoya, (Japan) aut Naito K. Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-01, Nagoya, (Japan) aut Journal of Radioanalytical and Nuclear Chemistry Articles Springer Netherlands 143/1(1990-11-01), 149-156 0236-5731 143:1<149 1990 143 10967 https://doi.org/10.1007/BF02117557 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02117557 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Matsui T. Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-01, Nagoya, (Japan) aut NATIONALLICENCE 700 1- Arita Y. Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-01, Nagoya, (Japan) aut NATIONALLICENCE 700 1- Naito K. Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Furo-cho, Chikusa-ku, 464-01, Nagoya, (Japan) aut NATIONALLICENCE 773 0- Journal of Radioanalytical and Nuclear Chemistry Articles Springer Netherlands 143/1(1990-11-01), 149-156 0236-5731 143:1<149 1990 143 10967 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer