Critical Current Density of Y-Ba-Cu-O Ceramics Prepared by the Coprecipitation Method and their Application to Superconducting Devices
The effect of the grain boundary formed in the sintering process on characteristics of critical current density (Jc) was investigated. The experiments were performed using samples prepared with a coprecipitated Y-Ba-Cu-O compound at a sintering temperature of 920 °C for 3 ∽ 100 hrs in O2. Though the packing density and superconducting volume fractions of the sample increased with increasing sin-tering time, Jc had a maximum value at a sintering time of around 12 hrs. A maximum Jc of 540 A/cm2 was obtained at 77K in zero field. Moreover, it was found that the magnetic field dependence of Jc which is indicative of “Josephson weak-link current” changed clearly with the sintering time. The temperature denendence of Jc showed that the grain boundary having S-N-S junctions at the initial stage of the sintering process, turned into S-I-S junction during prolonged sintering. Using this Y-Ba-Cu-0 ceramics, granular superconducting devices for optical detection were examined.
KeywordsSinter Process Critical Current Density High Magnetic Field Solid State Reaction Method Optical Detection
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