2-DIMENSIONAL BEHAVIOR AND CRITICAL CURRENT ANISOTROPY IN (BI,PB)2SR2CA2CU3O10+X TAPES

The critical current anisotropy I(c)(B,theta) of Ag-sheathed Bi-2223 tapes has been measured in detail at 77.3 K. We find that I(c)(B,theta) is influenced only by the c-component of the magnetic field and can thus be rewritten as I(c)(B.sin theta). This is considered as evidence for two dimensional behavior of this high-T(c) superconductor. The data do not follow this relationship anymore, if the angle theta between the field and the a,b-plane is smaller than about 10-degrees. Referring to published results on single crystalline films of Bi:2212, this is attributed to misalignments of the grains from the a,b-plane. After careful examination of the I(c)-B relationship up to 1.4 Tesla (both for B parallel-to c and for B parallel-to tape) and by dividing B(parallel-to c) by B(parallel-to tape) at the same I(c) level, we obtain an almost field independent constant, which corresponds to an angle of around 10-degrees. A comparison of different tapes reveals that the pinning ability plays the most important role for J(c) rather than the degree of texture, if the texture is good enough.