Abstract
Reaction kinetics for oxygen uptake into partially substituted YBa 2Cu 3O x are investigated. Materials studied include the Y 1−yLa yBa 2Cu 3O x system, YBa 2Cu 2.5Fe 0.5O x and Y 0.5Na 0.5Ba 2Cu 3O x. The reaction kinetics are found to decrease strongly on substitution at the copper site, but only vary mildly on substitution at the rare earth site. For Y 1−yLa yBa 2Cu 3O x a change in the rate law governing the oxygenation reaction is observed with y. We observe generally that Y 1−yLa yBa 2Cu 3O x with increasing y in a confined temperature range (around 400C) behaves similarly to YBa 2Cu 3O x with increasing temperature. This pertains to the change in rate law from linear to parabolic, as well as to initial decrease in activation energy, decrease in superconducting transition temperature and decrease in orthorhombic splitting. Correlations are accordingly drawn between structural detail, superconductivity, and kinetic parameters.
Published Version
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