Abstract
Ti, Zr and Hf doped MgB2 polycrystalline samples have been prepared by using a hot pressing technique. In Ti doped MgB2, it was found that the optimum concentration of Ti for the critical current density Jc was 5% and Jc value was improved from 1.9 x 10(5) A/cm2 (Ti 0%) to 5.6 x 10(5) A/cm2 (Ti 5%) in self-field at 10 K. Jc values were also improved to 5.0 x 10(5) A/cm2 with 2% Zr doping and to 4.8 x 10(5) A/cm2 with 1% Hf doping. We found that the improvement of the irreversibility field Birr with Zr and Hf doping was larger than that of Ti doping.