Improved superconducting properties in nanocrystalline bulk MgB_2

Abstract

Highly dense nanocrystalline MgB_2 bulk superconductors with distinctly improved pinning were prepared by mechanical alloying of Mg and B powders and hot compaction at ambient temperatures. The nanocrystalline samples reveal high critical current densities of 105 A/cm2 at 20 K and 1 T together with a strongly shifted irreversibility line towards higher fields resulting in H_irr(T) ~ 0.8 H_c2(T), whereas typically H_irr(T) ~ 0.5 H_c2(T) is observed for bulk untextured samples. These values exceed that of all other so far reported bulk samples and are in the range of the values of thin films. The improved pinning of this material which mainly consists of spherical grains of about 40-100 nm in size is attributed to the large number of grain boundaries.

14 pages including 4 figures

References in corpus (7)

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• Superconductivity in Dense $Mg{B}_2$ Wires
• Thin Film Magnesium Boride Superconductor with Very High Critical Current Density and Enhanced Irreversibility Field
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Cited by in corpus (20)

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• Limits of the upper critical field in dirty two-gap superconductors
• Universal relationship between crystallinity and irreversibility field of MgB2
• A Trapped Field of >3T in Bulk MgB2 Fabricated by Uniaxial Hot Pressing
• Mg(B,O)2 precipitation in MgB2
• Strong Pinning Enhancement in MgB2 Using Very Small Dy2O3 Additions
• Nanoscale grains, high irreversibility field, and large critical current density as a function of high energy ball milling time in C-doped magnesium diboride
• Microstructure and high critical current of powder in tube MgB2
• Significant enhancement of irreversibility field in clean-limit bulk MgB2
• Thermally-activated current transport in MgB_2 films
• Temperature dependence of trapped magnetic field in MgB2 bulk superconductor
• Defect structures in MgB2 wires introduced by hot isostatic pressing
• The Influence of Synthesis Parameters on Microstructures and Superconducting Properties of MgB2 Bulks
• Superconducting properties of nanocrystalline MgB${}_2$
• Correlated vortex pinning in Si-nanoparticle doped MgB2
• Improved Current Densities in MgB2 By Liquid-Assisted Sintering
• Improved Superconducting Properties in Bulk MgB2 Prepared by High Energy Milling of Mg and B Powder
• Comparative Study of Dense Bulk MgB${}_2$ Materials Prepared by Different Methods