Partial melt-processing and annealing of (Bi,Pb)-1212 superconductors

A partial melt process in oxygen atmosphere was established for the (Bi,Pb) -1212 compound. The formation of the 1212 phase is fast and leads to a dens e, isotropic microstructure with a phase purity of 90 vol%. No transport cr itical current density could be measured whether in as prepared nor in anne aled samples. However, inductive measurements of samples annealed in flowin g oxygen acid argon at temperatures between 400 degreesC and 1000 degreesC, revealed that critical temperature and irreversible magnetization are impr oved for reducing as well as oxidizing annealings. This points to the prese nce of two different superconducting phases. Highest T-c was 83 K for a sam ple with stoichiometry of Bi0.2Pb0.6Sr2Ca0.3Y0.7Cu2.05Oz annealed in flowin g argon at 750 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved .