Properties of Alloy Precursors and the Resulting Superconducting YBa sub 2 Cu sub 3 O sub 7-- delta --Ag Composites

• Published in: Journal of applied physics 1992-02, Vol.71 (3), p.1327-1335
• Main Authors: Early, E A, Simnad, M T, Maple, M B
• Format: Article
• Language: English
• ISSN: 0021-8979

A significant obstacle to the widespread application of high-temperature superconductors is the poor mechanical properties of these oxides. A novel processing technique was investigated that attempts to circumvent this problem using ductile alloy precursors to superconducting composites. Alloys of composition Y--2Ba--3Cu--Ag were prepared by arc- and induction melting the metals. A variety of mechanical tests shows that alloys with 90 wt.% Ag are ductile, and differential thermal analysis indicates a solidus temperature of 703 deg C. Using thermogravimetric analysis, the oxidation rate of Y--2Ba--3Cu--90 wt.% Ag alloys was studied. This rate does not follow that which is expected based upon the theory of internal oxidation, nor is there a transition to external oxidation upon lowering the partial pressure of oxygen. The superconducting properties of the oxide in the resulting composite are similar to those of polycrystalline samples, with a T sub c of 90K. Superconductivity is achieved only when the alloy is oxidized above the solidus temperature, where the presence of a liquid phase enables the oxides to be concentrated and connected.