Thermodynamic investigation of Cr2TeO6 and Cr2Te4O11

Abstract

Knowledge on thermodynamic stability of the compounds formed by the interaction of volatile fission products with the components of structural materials during reactor operation is important to predict life time of the nuclear fuel pin inside a nuclear reactor. In the present study, thermodynamic properties of two compounds viz., Cr2TeO6(cr) and Cr2Te4O11(cr) in Cr-Te-O system are reported. The standard molar Gibbs energy of formation of Cr2TeO6(cr) and Cr2Te4O11(cr) have been determined by EMF measurement technique employing galvanic cells: (-) Pt, C, Cr2O3(cr), Te(cr or l), Cr2TeO6(cr)│CSZ│O2(g) (pO2 = 0.21 atm), Pt (+) and (-) Pt, C, Cr2TeO6(cr), TeO2(cr), Cr2Te4O11(cr)│CSZ│O2(g) (pO2 = 0.21 atm), Pt (+), in the temperature range 685 ≤ T/K≤877 and 705 ≤ T/K≤843, respectively. The standard Gibbs energy of formation of Cr2TeO6(cr) and Cr2Te4O11(cr) derived from the measured EMF data could be expressed as: ΔfGº (Cr2TeO6, cr) (±5.6 kJ.mol−1) = -1644.2 + 0.5606 T (725 ≤ T/K≤877) and ΔfGº (Cr2Te4O11, cr) (±6.3 kJ.mol−1) = -2458.2 + 1.013 T (705 ≤ T/K≤843), respectively. The values of ‘third-law’ enthalpy of formation ΔHf,298Ko of Cr2TeO6(cr) and Cr2Te4O11(cr) are found to be -1632.2 ± 0.8 kJ mol-1 and -2432.4 ± 0.5 kJ mol−1, respectively.