Indexed on: 24 Dec '09Published on: 24 Dec '09Published in: Physics - Superconductivity
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 pining: 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 SiC-doped material exhibited jc= 1000000 A/sq. cm 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= 100 A/sq. cm in 10 T field). Materials synthesized from Mg and B taken up to 1:20 ratio were superconductive. The highest jc (60000 A/sq. cm at 20 K in zero field, Hirr= 5 T) and the amount of SC phase (95.3 percents 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 GPa and 13.08 GPa, at a load of 4.9 N, respectively).