[Zurück]

T. Prikhna, W. Gawalek, V. Tkach, N. Danilenko, Y. Savchuk, S. Dub, V. Moshchil, A. Kozyrev, N. Sergienko, M. Wendt, V. Melnikov, J. Dellith, H. W. Weber, M. Eisterer, C. Schmidt, T. Habisreuther, D. Litzkendorf, I. Vajda, A. Shapovalov, V. Sokolovsky, P. Nagorny, V. Sverdun, J. Kosa, F. Karau, A. Starostina:
"Effect of higher borides and inhomogeneity of oxygen distribution on critical current density of undoped and doped magnesium diboride";
Journal of Physics: Conference Series, 234 (2010), 012031; S. 1 - 14.

The effect of doping with Ti, Ta, SiC in complex with synthesis temperature on the
amount and distribution of structural inhomogeneities in MgB2 matrix of high-pressuresynthesized-
materials (2 GPa) which can influence pinning: higher borides (MgB12) and
oxygen-enriched Mg-B-O inclusions, was established and a mechanism of doping effect on jc
increase different from the generally accepted was proposed. Near theoretically dense SiCdoped
material exhibited jc= 106 A/cm2 in 1T field and Hirr =8.5 T at 20 K. The highest jc in
fields above 9, 6, and 4 T at 10, 20, and 25 K, respectively, was demonstrated by materials
synthesized at 2 GPa, 600 oC from Mg and B without additions (at 20 K jc= 102 A/cm2 in 10 T
field). Materials synthesized from Mg and B taken up to 1:20 ratio were superconductive. The
highest jc (6×104 A/cm2 at 20 K in zero field, Hirr= 5 T) and the amount of SC phase (95.3% of
shielding fraction), Tc being 37 K were demonstrated by materials having near MgB12
composition of the matrix. The materials with MgB12 matrix had a doubled microhardness of
that with MgB2 matrix (25±1.1 GPa and 13.08±1.07 GPa, at a load of 4.9 N, respectively).

http://dx.doi.org/10.1088/1742-6596/234/1/012031

http://publik.tuwien.ac.at/files/PubDat_190124.pdf