THE RESISTIVE TRANSITION IN HIGH MAGNETIC-FIELDS IN YBA2(CU1-XZNX)3O7-DELTA

We have investigated the resistive transition in a series of Zn substi tuted ceramic YBCO samples, both in zero field, and in fields up to 17 .5 T. We studied samples with Zn concentrations x of up to 10 %. The l owest T(c) was observed for x = 9%, where T(c) (R = 0) is at 700 mK. T he normal state resistance shows a linear temperature dependence down to the superconducting onset. For the x = 9 % Zn sample, this linear r egion extends to 1. 8 K. In magnetic fields the resistive transition b roadens considerably, and the R = 0 transition moves to below 100 mK. The resistive transitions can be understood in terms of thermally acti vated flux creep.