High transport critical current density and large Hc2 and Hirr in nanoscale SiC doped MgB2 wires sintered at low temperature

Authors

Saeid Soltanian, University of WollongongFollow
Xiaolin Wang, University of WollongongFollow
Josip Horvat, University of WollongongFollow
S X. Dou, University of WollongongFollow
M D Sumption, Ohio State University, USA
M Bhatia, Ohio State University, USA
Edward W. Collings, Ohio State University, USA
Paul G. Munroe, The University of New South Wales
M Tomsic, Hyper Tech Research Incorporated, USA

RIS ID

13694

Publication Details

Soltanian, S, Wang, X, Horvat, J, Dou, SX, Sumption, M, Bhatia, M, Collings, E, Munroe, P & Tomsic, M (2005), High transport critical current density and large Hc2 and Hirr in nanoscale SiC doped MgB2 wires sintered at low temperature, Superconductor Science and Technology, 18, pp. 658-666.

Abstract

We report a systematic study on the effect of sintering temperature on the phase formation, critical current density, upper critical field and irreversibility field of nanoscale SiC doped MgB₂. Bulk and Fe sheathed wires doped with different nano-SiC particle sizes have been made and heat treated at temperatures ranging from 580 to 1000 °C. A systematic correlation between the sintering temperature, normal state resistivity, RRR, J_c, H_c2, and H_irr has been found in all samples of each batch. Samples sintered at a lower temperature have a very fine and well consolidated grain structure while samples sintered at a high temperature contain large grains with easily distinguishable grain boundaries. Low temperature sintering resulted in a higher concentration of impurity precipitates, larger resistivity, higher J_c up to 15 T and lower T_c values. These samples show higher H_c2 and H_irr at T near T_c but lower H_c2 near T = 0 than samples sintered at high temperature. It is proposed that huge local strains produced by nano-precipitates and grain boundary structure are the dominant mechanism responsible for higher H_c2 at T near T_c. However, higher impurity scattering due to C substitution is responsible for higher H_c2 in the low temperature regime for samples sintered at a higher temperature. In addition to high H_c2, it is also proposed that the large number of nano-impurities serve as pinning centres and improve the flux pinning, resulting in higher J_c values at high magnetic fields up to 15 T.