Formation of Submicron-Thick Oxide Barrier for Reducing AC Loss in Multifilamentary Bi2223 Tapes

Synopsis: Bi2223 multifilamentary tapes with interfilamentary oxide barriers were fabricated and their AC loss properties were examined under AC external magnetic field. In order to avoid the side effect on Bi2223 phase formation during heat treatment, Ca 2 CuO 3 and SrZrO 3 with average grain sizes of 1-2 μm were selected as barrier materials. Furthermore, an additional Bi2212 powder corresponding to 20wt% were mixed with them to improve their deformation properties for cold working. The mixed oxide powders were introduced among the twisted Bi2223 filaments. The critical current densities (J c ) in the barrier tapes were 10-20% lower than those in the tapes without barriers. In a parallel field, the loss reduction in the SrZrO 3 /Bi2212 barrier tape is most remarkable because the continuity of the SrZrO 3 /Bi2212 barriers is far superior to the Ca 2 CuO 3 /Bi2212 barriers. At 50 mT around power-grid frequencies, parallel field losses in a twisted tape with SrZrO 3 /Bi2212 barriers are 80% lower than the nontwisted tape. From the frequency dependence of AC losses in a perpendicular field, it was confirmed that the transverse resistivity in the SrZrO 3 /Bi2212 barrier tape is 8-9 times higher than the tape without barriers. However, around the power-grid frequencies, the introduction of barrier reduces AC losses only slightly in a perpendicular field. The twist pitch of the present barrier tape (= 16 mm) is probably too long to decouple the filaments in a perpendicular field.

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Characterization of Ag-Sheathed Bi2223 Tapes with Interfilamentary Oxide Barriers AC Loss Reduction under AC Perpendicular Transverse Magnetic Field

Inada¹,

Okumura²,

Ohtsu³

et al. 2014

TEION KOGAKU

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Synopsis:Low AC loss Ag-sheathed Bi2223 tapes with oxide barriers among the twisted filaments were successfully fabricated using the powder-in-tube method. SrZrO 3 was selected as the barrier material for its compatibility with Bi2223 oxide.Moreover, a small amount of Bi2212 was mixed with SrZrO 3 to improve its ductility for cold working. By controlling barrier thickness and reducing the final tape width down to 2.7 mm, transport critical current densities J c at 77 K and self-field attained 17-23 kA/cm 2 for twisted barrier tapes with twist lengths L t between 4 and 9 mm. For barrier tape with the shortest L t = 4 mm, a coupling frequency f c , which is related to inverse of coupling time constant W c , of 270 Hz was attained in an AC transverse field perpendicular to a broader face of the tape. To our best knowledge, f c = 270 Hz under a perpendicular field is the highest ever reported value for Bi2223 tapes with self-field J c > 15 kA/cm 2 at 77 K. According to these achievements, perpendicular field losses around 50 Hz for barrier tape were 70-80% lower than those for conventional 4 mm-width tape with fully coupled filaments.

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Formation of Submicron-Thick Oxide Barrier for Reducing AC Loss in Multifilamentary Bi2223 Tapes

Cited by 3 publications

References 4 publications

Ac and Other Losses

Ac and Other Losses

Fabrication and AC Loss Properties of Bi2223 Tapes with Interfilamentary Barriers

Characterization of Ag-Sheathed Bi2223 Tapes with Interfilamentary Oxide Barriers AC Loss Reduction under AC Perpendicular Transverse Magnetic Field

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