Fabrication of 10,000A/cm2 Class Bi-2223 Sintered Bulk
Many kinds of preparation processes of calcined powder have been proposed for producing sintered bulk Bi-2223. We adopted a coprecipitatcd method that is able to form homogeneous and fine powders that lead to facilitating synthesis in the calcination and sintering reaction. However, calcination condition of coprccipitated powder for obtaining high Jc sintered bulk is delicate. Oxide superconducting calcined powder adsorbs firstly atmospheric moisture, then reacts with carbon dioxide, which aim deteriorate the superconducting properties of the oxide superconductor. Carbon that is included in the calcined powder segregates in crystal grain boundaries during sintering process. This segregation decreases Jc, by cause in weak links, preventing superconducting current from flowing across grain boundaries. We reconsidered the calcined powder preparation process. By improving a solvent removal method after a wet pulverizing method where moisture is easily adsorbed, it was possible to reduce the carbon content to under 0.03wt%. The calcined powder was pressed into 20 mm diameter pellets and then sintered at 850 °C for 50hr in air with an intermediate pressing by the CIP (cold isostatic press) method. The Jc of the sintered bulk was increased to be 10,000A/cm2, reproducibly.
KeywordsAtmospheric Moisture Plate Crystal Sinter Reaction Calcine Powder Isostatic Press
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