High-temperature heat capacities and electrical conductivities of UO2 doped with simulated fission products for 2–10 at% burnup

Thermophysical properties of uranium–europium mixed oxides

“…Such anomalous increase in the heat capacity is usually observed when UO 2 is doped with an aliovalent cation (in this case Eu +3 , Eu +2 ). This phenomenon was reported earlier [11][12][13][19][20][21][22][23][24][25] and has been ascribed to the formation of oxygen Frenkel defect pairs. An estimate of the temperature dependence of the heat capacity pertaining to the solid solutions (U 1y Eu y )O 2x (y = 0.2, 0.4, 0.6) over the temperature range 298-1800 K was obtained by extrapolating the expression derived through the least squares regression analysis of these data in the temperature range 298-900 K. This would hence forth be termed as baseline heat capacity.…”

Heat capacity measurements and XPS studies on uranium–lanthanum mixed oxides

“…The present observed heat capacity anomaly might also be due to predominant contribution of formation of Frenkel pairs of oxygen defects, as it was observed in our previous study on heat capacity of (U 1−y Gd y )O 2±x [11]. This is because the formation of large number of Frenkel-pair defects of oxygen is enabled when UO 2 is doped with aliovalent cations (La 3+ in this case) [4][5][6][7][8][9][10][11]. The baseline heat capacity of (U 1−y La y )O 2±x (y = 0.2, 0.4, 0.6, and 0.8) was obtained from a least squares fitting for the data in the temperature region 298-1200 K and extrapolating up to 1800 K. The baseline and combined heat capacity data were fitted using the following equations, respectively…”

“…500-600 K. This phenomenon was attributed to the formation of Frenkel-pair like defects of oxygen [4][5][6][8][9][10]. This is because the formation of large number of Frenkel-pair defects of oxygen is enabled, when UO 2 is doped with aliovalent cations (La 3+ in this case).…”

“…Heat capacity of uranium-rare earth mixed oxides has been determined by various authors [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Anomalous increase in the heat capacity with temperature was reported by various authors [3][4][5][6][7][8][9][10][11] whereas certain authors [12][13][14][15][16] reported no anomalous increase in the heat capacity. Earlier [11], we have measured the heat capacity of (U 1−y Gd y )O 2±x (y = 0.1, 0.2, and 0.5) by DSC in the temperature range 298-800 K. Considerable anomalous increase in the heat capacity was observed for (U 1−y Gd y )O 2±x with y = 0.1-0.5.…”