High Tc Bi2Sr2CaCu2Ox Superconducting Powder and Wires for High Field Magnets

This SBIR Phase II program will allow MetaMateria Technologies to further improve process methods for preparing Bi 2212 powder in order to establish a stable source of reliable starting powder for Bi-2212/Ag wire manufacturers and equipment developers. One objective of the High Energy Physics (HEP) magnet development program by DOE is the design and development of dipole magnets with fields greater than 15T. Promising candidates for high field applications in the 15T regime are the so-called High Temperature Superconductors (HTS), such as Bi2Sr2CaCu2Ox (Bi-2212) and YBa2Cu3Ox (YBCO) due to their high upper critical field. MetaMateria utilized a chemical synthesis approach using solution based techniques developed during a Phase I SBIR, which showed the most promise for making a high quality powder and this will be the focus during Phase II. A reliable source of powder with definable properties is needed for the stabilization of the wire manufacturing process, particularly to avoid the JE limiting defects are tied to the type of powder used for the Bi-2212/Ag wires. Performance of a wire depends upon the interplay between powder characteristics, wire drawing process variables and configuration, and thermal processing of the wire. The goal is a reliable starting powder to allow downstream stabilization of the wire manufacturing process. During Phase I, powder from different batches showed uniformity in composition and purity, however, carbon content was found to be higher than desired and several approaches will be used to lower this below 50 ppm during Phase II and hydrogen below 100 ppm. The resulting powder will be used by our partner OST (Oxford Superconductor Technology) will use to fabricate standard round filament wires that will then be characterized and tested. Efforts to minimize porosity due to gas evolution during thermal processing of wires will also be made. The microstructure and the performance of the wire will then be correlated with the powder characteristics. The engineering critical current density, JE, as a function of magnetic field will then be measured at 4.2 K. In phase II, the composition will be optimized to increase the current carrying capacity of the Ag-Mg sheathed Bi-2212 wire, since lack of time did not permit optimization studies in Phase I. Once processing conditions are established for making a higher quality powder, MetaMateria will scale up its processing techniques to make larger batches of powder (2-5 Kg). OST will further enhance the performance of the wire by examining alternative methods for preparing wires. Commercial Applications and Other Benefits: The successful completion of this SBIR program will address direct needs for the HTS conductor development community, where a growing concern exists for stable sources of starting powder that can provide performance required for high field magnets. Successful completion of the proposed program will enable availability of a reliable domestic source of stable powder which is critical for downstream process stabilization of Bi-2212/Ag composite wires.