AC Loss Properties in Bi2223 Multifilamentary Tapes with Enhanced Transverse Resistivity by Introducing Oxide Barriers
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1099-II04-07
AC Loss Properties in Bi2223 Multifilamentary Tapes with Enhanced Transverse Resistivity by Introducing Oxide Barriers Ryoji Inada1, Yoshiki Mitsuno1, Kazuma Soguchi1, Yuichi Nakamura1, Akio Oota1, Chengshan Li2, and Pingxiang Zhang2 1 Department of Electrical and Electronic Engineering, Toyohashi University of Technology, 1-1 Tempaku-cho, Toyohashi, 4418580, Japan 2 Northwest Institute for Nonferrous Metal Research, P.O.Box 51, Xi'an, 710016, China, People's Republic of ABSTRACT Bi2223 multifilamentary tapes with enhanced transverse resistivity by introducing Ca2CuO3 and SrZrO3 as interfilamentary barriers were prepared and their AC loss properties were examined under AC external magnetic field. To improve the deformation properties of these oxide powders, 20-30wt% Bi2212 powders were mixed with them. The mixed oxide powders were introduced among the twisted Bi2223 filaments by using dip-coating method. AC loss properties under AC parallel or perpendicular field were measured and compared with the results for the tape without barriers. The loss measurements were carried out by changing both the amplitude and the frequency of external field. Based on the experimental results, the effect of barrier introduction on the loss reductions was discussed. INTRODUCTION Ag-sheathed Bi2223 tapes fabricated by powder-in-tube (PIT) process are most applicable high-Tc superconducting wires for 77 K usage in the present stage, while RE123 (RE = Y, Gd, Sm…) coated conductors are under development. Although the critical current (Ic) above 100 A and the length of km-class are enough for the prototype configuration such as cables and transformers, their AC losses are still too high for the practical applications [1]. The large loss generation in AC external magnetic field is mainly attributed to the strong coupling among the Bi2223 filaments. This interfilamentary coupling is caused by the low resistivity of Ag-matrix and direct connection between the filaments by bridging. In order to decouple the filaments under AC external field and achieve significant AC loss reduction, not only twisting the filaments with a proper twist length but also increasing the transverse resistivity of filamentary regions is necessary [2-4]. The use of Ag-alloy with high resistivity as matrix [3,4] or introduction of highly resistive layers as barriers among each filament [4-11] is considered to be effective methods to increase the transverse resistivity. In this paper, we prepared Bi2223 multifilamentary tapes with enhanced transverse resistivity by introducing oxide barriers among the filaments and investigated their AC loss properties. EXPERIMENTAL DETAILS The conventional powder-in-tube process was used for the preparation of Bi2223 tapes with interfilamentary barriers. Oxide material usable as barrier should be highly-resistive and non-poisonous to the Bi2223 phase during sintering, as well as easily deformable during cold
Figure 1. Transverse cross sectional views of Bi2223 tapes with interfilamentary oxide barriers before sintering (
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