Gibbs Free Energy of Formation ofLnBa2Cu3O7-xPhases Determined by the EMF Method (Ln=Yb, Tm, Er, Ho, Dy)

Employing electrochemical cells with calcium fluoride solid electrolytepO2, CaO+CaF2//CaF2//CuO+LnBa2Cu3O7x+Ln2CuBaO5+BaF2,pO2, forLn=Yb, Er, Tm, Ho, Dy, and Gd, the Gibbs free energy change of the reaction of formation of the solidLnBa2Cu3O7-xphases for subsequent lanthanide elements was determined. Either an air or argon and oxygen gas mixture was used to fix oxygen 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 investigatedLnBa2Cu3O7-xphases, except for that of the gadolinium compound. In this particular case, the side reaction made the reproducible cell performance impossible.