GIBBS FREE ENERGY OF FORMATION OF LnBa2Cu3O7-x PHASES DETERMINED BY THE EMF METHOD (Ln=Yb, Tm, Er, Ho, Dy)

摘要

Employing electrochemical cells with calcium fluoride solid electrolyte pO2, CaO+CaF2//CaF2//CuO+LnBa2Cu3O7-x+Ln2CuBaO5+BaF2, pO2, for Ln=Yb, Er, Tm, Ho, Dy, and Gd, the Gibbs free energy change of the reaction of formation of the solid LnBa2Cu3O7-x phases for subsequent lanthanide elements was determined. Either an air or Ar and O gas mixture was used to fix O potential over the reference and working electrodes. Next, the obtained results were used to derive the Gibbs free energy change of reactions of formation of the investigated LnBa2Cu3O7-x phases, except for that of the Gd compound. In this particular case, the side reaction made the reproducible cell performance impossible. 22 refs.