ANGULAR-DEPENDENCE OF CRITICAL CURRENTS AND GRAIN MISALIGNMENT IN AG CLAD (BI,PB)(2)SR2CA2CU3O10 TAPES

Two-dimensional behaviour of the critical current in highly textured silver clad (Bi,Pb)(2)Sr2Ca2Cu3O10 tapes was observed and analysed by introducing an effective grain misalignment angle, phi(eff). This angle was found by SEM to be identical to the average crystallographic grain misalignment angle in the superconducting core. Furthermore, after fast neutron irradiation, which is isotropic, the J(c) of the tapes were modified by the introduction of artificial defects, but the phi(eff) remained the same. This proves that the crystallographic misalignment of the grains determines the critical current anisotropy of the tape in a magnetic field, i.e. I-c(B parallel to tape plane) scales with I-c(B perpendicular to tape plane) with the factor sin phi(eff). Therefore, phi(eff) is an intrinsic property of the tape. phi(eff) is found to be around 10 degrees in different samples. We propose that this typical value is determined by intrinsic mechanical properties of the (Bi,Pb)(2)Sr2Ca2Cu3O10 compound and is a result of the mechanical deformation of the tape during the tape fabrication. From a comparison of different samples, we propose that the: pinning ability is the determining factor of J(c) when phi(eff) is small enough.