Evaluation of field-angle anisotropy of critical current in multifilamentary Bi-2223 tapes prepared by CT-OP process

Abstract

The critical current property of Bi-2223 silver sheathed tape has been significantly improved by application of ConTrolled Over Pressure (CT-OP) process with adjusting temperature and oxygen partial pressure at the final heat treatment. In this paper, the field-angle dependence of the critical current density was measured at 77.3 K and the crystalline misorientation angle was estimated for four specimens with different critical current densities. It is found that in a parallel magnetic field, the critical current density of the latest Bi-2223 tape of 190 A class is remarkably higher than the other specimens over a wide region of magnetic field. On the other hand, although the critical current density of the latest tape in a normal magnetic field is higher than the other specimens, the difference is relatively small especially at high magnetic fields. Thus, the field-angle anisotropy of the latest tape is higher than the other specimen. The observed results can be explained by the improved condensation energy density and the better c-axis alignment in the latest tape.