ONE-STEP REACTION AND CONSOLIDATION OF HG BASED HIGH-TEMPERATURE SUPERCONDUCTORS BY HOT ISOSTATIC PRESSING

A hot isostatic press (HIP) technique has been used successfully to re act and consolidate in one step the Hg based high-temperature supercon ductors (HTS's). Hot isostatic pressing (HIPping) overcomes some of th e problems encountered in the quartz-encapsulation technique typically used to make Hg based HTS samples, such as containing the high vapor pressures of Hg and avoiding explosions. The HIPping conditions for pr ocessing (i.e., range of temperature and pressure) are significantly d ifferent from those used in the quartz-encapsulation method. These dif ferences seem to relax the stringent conditions on precursor processin g required in other processing methods. Hg based I-ITS samples were su ccessfully made from both nitrate and carbonate precursors, as well as from commercially available precursors. X-ray diffraction experiments indicated that the best materials were made with nitrate precursors a nd were composed of 1223 phase (66%), 1212 phase (33%) and a small amo unt of BaCuO2 (1%). We have HIPped powders and contained them in selec ted high-purity metal foils. We find that Au is a good containment mat erial for processing as it reacts very little with the Hg compounds be ing formed. Ag, on the other hand, reacts extensively. Samples with de nsities as high as 97% of theoretical density were formed. This techni que has been used to successfully fabricate components that may lead d irectly to devices.