TRANSPORT CRITICAL-CURRENT AT 4.2 K OF PURE AND MGO-DOPED BI-2212 TAPES

2x3.5 mu m thick Pi 2212 tapes have been prepared by oxidation reactio n of precursors deposited electrolytically in a sequential way on both sides of a 50 mu m thick Ag tape. To try and increase their critical current density MgO doping was attempted. For the sake of making the c omparison as differential as possible a sample of Bi 2212 precursors w as prepared by electrodeposition. Part of it was directly heat treated , whereas the left was electrolytically plated before with MgO to get the average composition Bi2Sr2Ca1Cu2Mg0.1. It was found that the trans port Jc 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 rat io of Jc(B parallel to (a,b)) to Jc(B perpendicular to (a,b)) starting from 1 for zero applied field was observed to reach 2 in a 7T field. Finally, the pinning potential of the two materials were determined ac counting for the silver backing correction (dependence of silver resis tivity as a function of magnetic field is incidentally presented too).