Thermodynamic and nonstoichiometric behavior of promising Hi-Tc cuprate systems via EMF measurements: a short review.

摘要

Electromotive force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on the YBa(sub 2)Cu(sub 3)O(sub x), GdBa(sub 2)Cu(sub 3)O(sub x), NdBa(sub 2)Cu(sub 3)O(sub x) and bismuth cuprate systems in the temperature range (approximately)400-750 C by means of an oxygen titration technique with an yttria-stabilized zirconia electrolyte. The shapes of the 400 C isotherms as a function of oxygen stoichiometry for the Gd and Nd cuprate systems suggest the presence of miscibility gaps at values of x that are higher than those in the YBa(sub 2)Cu(sub 3)O(sub x) system. For a given oxygen stoichiometry, oxygen partial pressures above GdBa(sub 2)Cu(sub 3)O(sub x) and NdBa(sub 2)Cu(sub 3)O(sub x) are higher (above x=6.5) than that for the promising YBa(sub 2)Cu(sub 3)O(sub x) system. A thermodynamic assessment and intercomparison of our partial pressure measurements with the results of related measurements will be presented.