Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 ex-situ tapes
arXiv:0807.4078 · doi:10.1063/1.3021468
Abstract
Ex-situ Powder-In-Tube MgB2 tapes prepared with ball-milled, undoped powders showed a strong enhancement of the irreversibility field H*, the upper critical field Hc2 and the critical current density Jc(H) together with the suppression of the anisotropy of all of these quantities. Jc reached 104 A/cm2 at 4.2 K and 10 T, with an irreversibility field of about 14 T at 4.2 K, and Hc2 of 9 T at 25 K, high values for not-doped MgB2. The enhanced Jc and H* values are associated with significant grain refinement produced by milling of the MgB2 powder, which enhances grain boundary pinning, although at the same time also reducing the connectivity from about 12% to 8%. Although enhanced pinning and diminished connectivity are in opposition, the overall influence of ball milling on Jc is positive because the increased density of grains with a size comparable with the mean free path produces strong electron scattering that substantially increases Hc2, especially Hc2 perpendicular to the Mg and B planes.
26 pages, 9 figures, submitted to J. Appl. Phys
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- Towards the Realization of Higher Connectivity in MgB2 Conductors: In-situ or Sintered Ex-situ?
- Study of the MgB2 grain size role in ex-situ multifilamentary wires with thin filaments
- Critical current density and microstructure of iron sheathed multifilamentary Sr1-xKxFe2As2/Ag composite conductors
- High-energy ball milling and synthesi temperature study to improve superconducting properties of MgB2 ex-situ tapes and wires
- In-situ high energy synchrotron X-ray diffraction investigation of the MgB2 phase formation and MgB2 tapes sintering
- High temperature heat treatment of B precursor and P.I.T. process optimization to increase Jc performances of MgB2-based conductor