Effects of oxide particle addition on superconductivity in nanocrystalline MgB2 bulk samples

✍ Scribed by Olaf Perner; Wolfgang Häßler; Jürgen Eckert; Claus Fischer; Christine Mickel; Günter Fuchs; Bernhard Holzapfel; Ludwig Schultz

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 675 KB
• Volume: 432
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2005.07.005

✦ Synopsis

In order to improve the extrinsic superconducting properties of MgB 2 a combination of nanocrystalline microstructure and particle doping was studied with regard to the enhancement of flux pinning. For comparison, MgO and SiO 2 particles were separately introduced into the MgB 2 matrix by the in situ preparation technique of mechanical alloying. The oxides do not affect the formation of MgB 2 but influence characteristically the critical current density J c and the irreversibility field H irr in hot pressed bulk samples due to a change of microstructure and lattice constants. Optimal doping levels are 5 wt.% for MgO and 2 wt.% for SiO 2 addition, which lead to improved J c values of 1.3 • 10 6 and 1.2 • 10 6 A/cm 2 in self-field at 7.5 K, respectively, but do not affect the critical temperature T c . Microstructural investigations revealed a nanocrystalline MgB 2 matrix with homogeneously distributed impurity particles.