Measurement of the gibbs energy of formation of URh₃ using an oxide solid electrolyte

Abstract

The Gibbs energy offormation of the intermetallic compound URh3has been measured in the temperature range 980 to 1320 K using an oxide solid state cell incorporating yttria-doped thoria as the solid electrolyte and a mixture of manganese and manganese oxide as the reference electrode. The cell can be represented as Pt, Mn+MnO I (Y₂0₃)Th0₂ URh+URh₃+U0₂+x URh, Pt The reversible emf of the cell was a linear function of temperature E = 15.60+0.0237/T(±0.8) mY. Using auxiliary thermodynamic data for MnO and U0₂+x the Gibbs' energy of formation of URh₃ from component metals has been computed. The results can be expressed by the equation L.G<URh3>=-316240+13.22/T(±3000) J mol^-1. The "third-law" enthalpy of formation of URh3at 298 K is-293.2 (±4) kJ mol^-1, significantly more negative than the value of -181.5 kJ mol^-1 calculated using Miedema's model.