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Uranium–europium mixed oxides (U1-yEuy)O2-x (y=0.2–0.8) were prepared by the citrate gel combustion technique and characterized by X-ray diffraction (XRD). Single phase fluorite structure was observed in those solid solutions with y≤0.6. The solid solutions with y>0.6 were found to be biphasic, with the second phase being cubic Eu2O3. Heat capacity and enthalpy increment measurements were carried out by using differential scanning calorimeter (DSC) and drop calorimeter in the temperature range 298–800K and 800–1800K, respectively. The Cp,m values at 298 K for (U1-yEuy)O2-x (y=0.2, 0.4, 0.6) are 64.8, 64.6, and 63.5 J·K-1·mol-1, respectively. An anomalous increase was observed in the heat capacity in all of the solid solutions with the onset temperature around 950 K. This could be attributed to the contribution from Frenkel pair oxygen defects. From the excess heat capacity data, the enthalpy for the formation of these defects was computed and found to be in the range of 2.10±0.02 eV.


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Thermophysical properties of uranium–europium mixed oxides

Show Author's information R. VENKATA KRISHNANR. BABUAbhiram SENAPATIG. JOGESWARARAOK. ANANTHASIVAN( )
Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, Tamil Nadu, India

Abstract

Uranium–europium mixed oxides (U1-yEuy)O2-x (y=0.2–0.8) were prepared by the citrate gel combustion technique and characterized by X-ray diffraction (XRD). Single phase fluorite structure was observed in those solid solutions with y≤0.6. The solid solutions with y>0.6 were found to be biphasic, with the second phase being cubic Eu2O3. Heat capacity and enthalpy increment measurements were carried out by using differential scanning calorimeter (DSC) and drop calorimeter in the temperature range 298–800K and 800–1800K, respectively. The Cp,m values at 298 K for (U1-yEuy)O2-x (y=0.2, 0.4, 0.6) are 64.8, 64.6, and 63.5 J·K-1·mol-1, respectively. An anomalous increase was observed in the heat capacity in all of the solid solutions with the onset temperature around 950 K. This could be attributed to the contribution from Frenkel pair oxygen defects. From the excess heat capacity data, the enthalpy for the formation of these defects was computed and found to be in the range of 2.10±0.02 eV.

Keywords: solid solution, uranium, europium, calorimetry, heat capacity, Frenkel defects

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Publication history

Received: 16 April 2015
Revised: 12 May 2015
Accepted: 18 May 2015
Published: 22 September 2015
Issue date: April 2015

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