Superconductivity in porous MgB2

Abstract

Porous magnesium diboride samples have been prepared by the heat treatment of a pressed mixture of Mg and MgB2 powders. It was found that linked superconducting structure is formed down to the minimum normalized density gamma= d/do= 0.16 (percolation threshold), where d is the density of MgB2 averaged over the sample, do= 2.62 g/cm3 is the X-ray density. Lattice parameters and critical temperature of the porous sample decrease with increasing porosity (decreasing gamma) and Tc2= 32K is minimal at gamma= 0.16. The grain boundaries in the porous samples are transparent for the current and Jc~3.105A/cm2 in self field at T= 20K in the samples with gamma~ 0.24.

6 pages, 4 figs. We have made principal changes in the results discussion. Paper has been accepted for publication in Solid State Communications (2006)

References in corpus (10)

• Thin Film Magnesium Boride Superconductor with Very High Critical Current Density and Enhanced Irreversibility Field
• Superconducting Properties of MgB2 Bulk Materials Prepared by High Pressure Sintering
• Current percolation and anisotropy in polycrystalline MgB${}_2$
• Carbon solubility and superconductivity in MgB2
• The influence of microstructures and crystalline defects on the superconductivity of MgB2
• Mg(B,O)2 precipitation in MgB2
• Transport - and inductive critical current densities in superconducting MgB2
• Microstructure and superconducting properties of hot isostatically pressed MgB2
• Microstructure and high critical current of powder in tube MgB2
• Superconducting properties and c-axis superstructure of Mg1-xAlxB2

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• Highly Porous Superconductors: Synthesis, Research, and Prospects
• Connectivity and Critical Currents in Polycrystalline MgB2
• The influence of weak texture on the critical currents in polycrystalline MgB${}_2$