Transport critical current at 4.2 K of pure and MgO-doped Bi 2212 tapes

2/spl times/3.5 /spl mu/m thick Bi 2212 tapes have been prepared by oxidation reaction of precursors deposited electrolytically in a sequential way on both sides of a 50 /spl mu/m thick Ag tape. To try and increase their critical current density MgO doping was attempted. For the sake of making the comparison as differential as possible a sample of Bi 2212 precursors was prepared by electrodeposition. Part of it was directly heat treated, whereas the left was electrolytically plated before with MgO to get the average composition Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/Mg/sub 0.1/. It was found that the transport J/sub c/ at 4.2 K of the MgO-doped specimen was about 1.4 times higher than that of the other in self field conditions and remained still 1.1 times higher in a 7 tesla field applied normally to the tape. The ratio of J/sub c/(B/spl par/(a,b)) to J/sub c/(B/spl perp/(a,b)) starting from 1 for zero applied field was observed to reach 2 in a field. Finally, the pinning potential of the materials were determined accounting silver backing correction (dependence resistivity as a function of magnetic field is incidentally presented too).