Effect of additives on the morphology and superconductivity of YBa2Cu3O(6+x) ceramic superconductors

The effects of the additives Al2O3 and Ag2O on the grain size and superconductivity of ceramic superconductors, of which YBa2Cu3O(6+x) is typical, are studied. While sintering treatments of such substances are necessary to create reasonably dense materials, sintering can result in an undesireable degree of grain growth, inhibiting superplastic deformation and consequently making application of the superconductor in hardware difficult. The effect of various weight percents of the additives on grain size and superconductivity was determined by microstructural examinations and measurements of electrical resistance versus temperature. Experiments have shown that the addition of Al203 powder during the sintering process constrained and reduced grain size, yet adversely affected the superconducting transition temperature of the ceramic. Ag2O, however, improved the superconducting transition temperature by several degrees, even when added as powders to the ceramic in amounts of up to 25 weight percent.