Abstract
Electromotive force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on lead-doped and lead-free superconducting ceramics in the temperature range ∼700–815°C by means of an oxygen titration technique. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. Thermodynamic assessments of the partial molar quantities ΔH(O 2) and ΔS(O 2) for lead-doped Bi-2212 and lead-free Bi-2212 indicate that the solid-state decomposition of these bismuth cuprates at low oxygen partial pressure can be represented by the diphasic CuO Cu 2O system. Comparison of these results with lead-doped Bi-2223 in powder and silver sheath form will be presented.
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