Effect of adding MgO to bulk Bi2212 melt textured in a high magnetic field

Bulk samples of Bi2212 pure and doped with MgO or SrSO4 were prepared by melt processing in a high magnetic field. The structure of the samples was analysed using XRD and SEM and their transport properties were studied. The results show that when a magnetic field is applied during melt processing the bulk Bi2212 is textured with the c-axis parallel to the field direction. The addition of MgO induces an improvement in the material properties. This is not observed using SrSO4. A significant improvement is observed at 77 K in the critical current density in self-field and in an external magnetic field. This improvement can be related to the better texturation obtained when MgO is added: it maintains high viscosity during melt processing and thus the texturation induced by the magnetic field is not weakened by liquid-phase spreading. The addition of MgO also induces a decrease in volume of residual phases. The improvement in properties in an external magnetic field can be attributed to a better indirect vortex pinning due to submicron MgO-rich inclusions in the superconducting matrix.