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

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 data on uranium-europium mixed oxides with europium content of 4.4 and 9.0 mol% have been reported by Matsui et al [10]. These authors have observed anomalous increase in the heat capacity, which sets in at temperatures ranging from 950 to 1150 K. Such an anomalous increase in the heat capacity observed in UO 2 doped with rare earth oxides (REO 1.5 , RE = La, Gd, Nd) has been reported in our earlier works [11][12][13]. Matsui et al [10] reported the heat capacity measured by using direct heating pulse calorimetry in the temperature range 300-1550 K for  (U 1y Eu y )O 2x (y = 0.044-0.09).…”

“…Temperature, heat flow, heat flow rate, and -lag calibrations were carried out, as explained in our previous publications [11,14,15]. The uncertainty in the heat capacity data measured by the DSC was estimated to be about 2%-3% based on our previous measurements on standard ThO 2 samples [15].…”

“…SETARAM. The procedures used in the measurement of heat capacity and enthalpy increment are described elsewhere [11][12][13][14][15].…”

“…4. The difference between these values of the heat capacity is termed as the excess heat capacity ( p C  ) [10][11][12][13]. The temperature dependence of this excess heat capacity is shown in Fig.…”