Effect of additives on the morphology and superconductivity of YBa2Cu3O6+x ceramic superconductors

Superplastic deformation is being studied as a means to turn the new ceramic superconductors into useful hardware. Superplastic deformation can occur when a small grained material is subjected to stress at temperatures that are at least a half of their melting point. The ceramic superconductors, of which YBa2Cu3O6+x is typical, require sintering treatments to create reasonably dense materials. However, sintering can result in a degree of grain growth that will not benefit superplastic deformation. To resolve the conflict of the need for full density with the need for a small grain size, the use of separate additives of Al2O3 and Ag2O particles to inhibit grain growth during sintering has been studied. The YBa2Cu3O6+x starting ceramic powders were made by the calcining of Y2O3, CuO, and BaCO3. Al2O3 and Ag2O were added as powders to the ceramic in amounts of 1, 5, 10, and 15 weight percent and 5, 15, 20, and 30 weight percent, respectively. The effect of the additions on grain size and superconducting performance were determined by microstructural examinations and measurements of electrical resistance versus temperature