OXIDATION REDUCTION AND OTHER GAS SOLID REACTIONS OF HIGH-TC SUPERCONDUCTORS

Understanding and controlling the reactions of the high-T(c) superconducting oxides with their gaseous environment are critical to attaining and preserving the optimal performance of the materials and resulting devices. These important interactions fall in two general classes. The first is concerned with the reversible exchange of oxygen between the oxide and the atmosphere at temperatures above about 300-degrees-C. These oxidation-reduction phenomena establish the oxygen content of the solid and hence its intrinsic electrical and magnetic properties. The second category concerns the reaction of the superconductor with the ambient gases to produce undesired products initially at the surface or grain boundaries, analogous to corrosion. These products, along with the overall microstructure, impurities, defects, etc., determine the effective electrical properties.