Standard Gibbs free energy of formation of the high-Tc superconducting compound YBa2Cu3O6.5+δ

Cells were constructed with a single-crystal CaF2 solid electrolyte and the cell EMF was measured. The standard change in free energy of formation of BaCuO2 (011 phase) and YBa2Cu3O6.5+δ (123 phase) from the constituent oxides was estimated. The oxygen non-stoichiometric fraction, δ, was taken into account in the estimation of ΔG123+δ0.