Improved Bi-2212/Ag Performance as a Competitor to Bi-2223/Ag in High-Tc Superconductor Wire Applications
The performance of Bi-2212 monofilament tape, produced by the powder-in-tube technique and a decomposition — recovery melt process, was significantly improved by employing an optimum dual atmosphere heat treatment. The atmosphere consists of nitrogen and oxygen applied alternatively at various stages during the process, and results in oxygen vacancies within the well aligned crystallites.
The investigation was carried out on short (50mm) samples, having a cross-section area of the ceramic core in the range 2×104µm2 – 5×104µm2.
An increase in the transport critical current Ic of up to 11A at 77K and up to 68 A at 4.2K in zero field (luAVcm electric field criterion) has been achieved, yielding a current caring capacity Jc in the range (2–4)×104A/cm2 at 77K and (1–3)×105A/cm2 at 4.2K.
The pinning energy is weaker than in the Bi-2223 tapes, but almost identical to the Bi-2212 epitaxial films. This, combined with a “one deformation — one heat treatment (∼30 h)” procedure, makes 2212 a strong competitor for low temperature wire applications.
KeywordsCritical Current Density Twist Boundary Broad Face Flux Creep Electric Field Criterion
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