Powdered and sintered samples – pure, substituted or doped - were prepared and characterized through magnetic measurements performed from 5K up to a few degrees above the transition temperature of about 39K. For all the samples, the irreversibility line appeared to be much lower than the HC2–T line and very far from those of high-TC and low-TC materials; thus indicating the need to increase pinning in the material. It was verified, using various procedures, that the sintered samples behaved as well-connected bodies, with no trace of granularity. Therefore, the critical current density values could be obtained by applying the critical-state model. Hysteresis loop measurements permitted the estimation of JC for both powders and for sintered samples, and confirmed the strong field decrease of JC which was implicit in irreversibility line behavior. An attempt was made to introduce defects into the MgB2 structure via various chemical treatments such as the substitution of Li at Mg sites and doping of the precursor B powders with Al and Si. The JC value always increased in doped or substituted samples (up to a factor 3), and this was significant; in the light of the small levels of substitution or doping which were used. The best result in terms of JC was achieved by Si-doping, which also did not significantly decrease the transition temperature.

Magnetic Characterization of Sintered MgB2 Samples - Effect of Substitution or ‘Doping’ with Li, Al and Si. M.R.Cimberle, M.Novak, P.Manfrinetti, A.Palenzona: Superconductor Science and Technology, 2002, 15, 43-7