MgB₂Thin Films Fabricated by a Precursor and Post-annealing Method Have a HighJ_cin High Magnetic Fields

Abstract

The critical current densities (Jc) of MgB2 thin films deposited on α-Al2O3 fabricated by a precursor and post-annealing process have been investigated in high magnetic fields of up to 30 T. Jc values of 2.8×105, 3.0×104, and 3.7×103 A/cm2 were obtained at 4.2 K in external magnetic fields of 10, 20, and 26 T respectively, applied parallel to the film surface. These values were comparable to those seen for Nb3Sn in fields up to 18 T, and surpassed them in fields over 18 T. The superconducting transition temperature was Tconset=29.6 K and Tczero=28.5 K. Grain connectivity was estimated to be 38.4%. The Hc2(0) estimated from the resistivity measurements was 45 T. Transmission electron microscope (TEM) observations of the microstructures suggested that grains 10–20 nm in size exist that show no epitaxial growth relationship to the sapphire substrate. Jc enhancements in fields up to ∼26 T are due to the strong grain boundary pinning associated with the small grains and the small size of MgO precipitates.

Magnesium diboride(MgB2) wires for applications

“…Quite interestingly, even at 20 K, J c of the malic acid wire was much higher than that of the un-doped wire. Even though, the J c of the malic acid wire is slightly better than that of the best commercial Mg 1.15 B 2 -SiC wire reported so far, it is still has room for further improvement compared with MgB 2 thin films [21,23].…”

Development and Prospects for the Future of Superconducting Wires

“…I hope that further research and development with the aim of meeting the above requirements in addition to J c improvement will lead to the practical applications of superconducting wires in future. 17) a Mg-diffusion-processed MgB 2 wire, 18) a PLD-processed MgB 2 thin film, 19) a Nb-Ti wire, and a Nb 3 Sn wire are also shown. …”

Superconducting properties of C-doped MgB2 thin film fabricated by the precursor and post-annealing method using the PLD process

“…We prepared carbon-doped films fabricated by the precursor and post-annealing method [10,11]. The precursor films were deposited on sapphire substrates by the conventional PLD method using KrF excimer laser at room temperature in a vacuum chamber.…”

“…In this report, the superconducting properties were investigated for C-doped MgB 2 thin films fabricated by precursor and postannealing method [9][10][11], in which a precursor film fabricated by pulse laser deposition (PLD) was post-annealed.…”