The effect of MgO addition on the formation and the superconducting properties of the Bi2223 phase

MgO particles were introduced into (Bi,Pb)(2)Sr2Ca2Cu3O10+delta powder in various weight fractions. Bulk samples were made from the Bi2223/MgO powder and heat-treated at various temperatures. The phase formation and the microstructure were studied for different amounts of MgO and for different sintering conditions. It was found that, below 845 degreesC, the ratio of Bi2223 phase decreased when the amount of MgO increased. The addition of MgO caused the Bi2201 phase content to decrease via an increase of the liquid viscosity. The presence of MgO influenced the microstructure of the samples and decreased the mean size of Bi2223 grains. The effects of the MgO addition on the intergranular critical current density, J(c) as a function of magnetic field was investigated by magnetisation hysteresis measurements. MgO presence significantly expands the magnetisation hysteresis loop and thus increases J(c) for amount of MgO, which does not exceed 15 wt.%. (C) 2002 Elsevier Science B.V. All rights reserved.