Effect of Various Intermediate Deformation Techniques on Jc and Grain Texture for Ag/Bi-2223 Tapes.

Three Ag sheathed Bi-2223 multifilamentary tapes were produced by a processing method that consists of two sintering treatments with an intermediate deformation, involving sandwich rolling (SR), pressing (P), or normal rolling (NR). The magnetic field dependence of the critical current density J_c was measured with the magnetic field H applied parallel to both the ab plane ( H | ab) and the c-axis ( H | c) of the Bi-2223 grains. Experimental results show that J_c of the pressed (P) tape ( J_cP) for both H | ab and H | c is about 1.5–1.8 times higher than that for the NR tape ( J_cNR) and the SR tape, although J_cSR is always larger than J_cP. The ratio of J_cSR/ J_cNR for H | c increases rapidly with the applied magnetic field and reaches a maximum of about 12 at μ₀ H ≥ 900 T. The calculated density of the pinning force F as a function of magnetic field shows that curves of F for SR, NR, and P tapes all have their maximum F_max at different magnetic fields and the magnitudes of F_max are also different from each other. The SR tape has the largest value of F_max, while NR has the smallest. XRD analysis shows that an intermediate deformation can destroy the grain alignment, and the larger the deformation, the worse the grain texture will be. Our experimental results, however, clearly show that J_c for Bi-2223 multifilamentary tapes is independent of grain alignment. The significant differences in J_c for tapes processed using the three different intermediate deformation procedures are dependent on the density of the pinning force and cannot be attributed to the grain alignment. Our experimental results support the view that SR processing is the best method for fabricating Ag/Bi-2223 tapes of high quality. [ABSTRACT FROM AUTHOR]