Key words: Bi2223 tapes; interfilamentary oxide barriers; filament twisting; ... grain size below 1 μm was used as barrier materials, and additional ... other hand, the R2223 values in all tapes after full reaction ... previous study[11], it was confirmed that in barrier tapes ... fine structure would be attributed to the improvements.
Progress in reducing AC magnetization losses of Bi2223/Ag tapes by introducing interfilamentary oxide barriers Ryoji INADA1, Akio OOTA1, Cheng-shan LI2, Ping-xiang ZHANG2 1. Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan; 2. Northwest Institute for Nonferrous Metal Research, P.O. Box 51, Xi’an 710016, China Received 23 August 2010; accepted 23 October 2010 Abstract: This paper presents our recent progress for the development of low-loss Bi2223/Ag tapes with interfilamentary oxide barriers. For the compatibility with Bi2223 superconductors, SrZrO3 was selected as barrier material. Moreover, small amount of Bi2212 was mixed with SrZrO3 to improve its ductility for cold working. By controlling the thickness of barrier layers among the filaments, reducing the tape width (104 A/cm2. With an additional effect of reducing wtape (from 4 to 2.7 mm), it is also confirmed that the loss values at 10−50 mT for the twisted barrier tapes are 60%−70% lower than those for the reference tape with wider wtape=4 mm. In order to examine the loss generation mechanism further, Figure 7 shows the normalized loss factors qm=μ0Qm/(2B02Stape) for both non-twisted tape and barrier tape with Lt=4 mm at different fixed operating frequencies fop from 30 to 105 Hz, as a function of perpendicular field amplitude B0. qm curve derived from the analytical prediction of hysteresis loss Qh for fully coupled filaments using an elliptical model approximation is also plotted[16]. Here, B0 at which qm shows a maximum is defined as a parameter Bmax. Bmax nearly corresponds to the full penetration field Bp for the tape and changes depending on the conditions for filament coupling under AC fields. As can be seen, all qm values at different fop for non-twisted tape nearly fall on one curve and Bmax well agrees with the prediction for fully coupled filaments (Fig.7(a)). On the other hand,
Bmax for twisted barrier tape is approximately 70% lower than the prediction for fully coupled state and nearly independent on fopfc, which is expressed as follows[18−19]: Qc ∝
1
sinh( π ωτ c 2 ) − sin( π ωτ c 2 )
π ωτ c 2 cosh( π ωτ c 2 ) + cos( π ωτ c 2 )
(4)
Here, we use the latter expression to describe the frequency dependence of Qc for our twisted barrier tape. On the other hand, as mentioned above, Qh for our barrier tape at fixed B0 is nearly independent on fop10 mT. This is the typical behavior of Qh at B0>Bp. On the other hand, Qc is nearly proportional to B02, which is expected from theoretical prediction[17−19]. It is also evident that Qc at 45 Hz is nearly the same level with Qh and total Qm is two times higher than Qh at B0>30 mT. This suggests that around 50 Hz, the loss reduction of our twisted barrier tape is still limited by significant Qc contribution. In order to obtain more remarkable loss reduction effect and also to maintain the effect in higher B0 range (∼0.1 T) in future, both further increasing coupling frequency fc to reduce Qc and improving Jc to enhance the fraction of Q h component in total Q m should be
Fig.9 Comparison of hysteresis loss Qh, coupling loss Qc and total magnetization loss Qm at 77 K and 45 Hz for twisted barrier tape with Lt=4 mm, as a function of perpendicular field amplitude B0
necessary. For remarkable improvement in electromagnetic performance (fc and Jc) for twisted barrier tapes, the optimization of fabrication process and tape structure (tape width, barrier thickness and twist pitch length) is currently being studied.
Ryoji INADA, et al/Progress in Natural Science: Materials International 20(2010) 104−110
110
4 Conclusions Our recent activities for the development of low-AC loss Bi2223 tapes with interfilamentary SrZrO3+Bi2212 as resistive barriers were presented. By controlling coating thickness of oxide barriers before stacking, reducing the tape width (12 kA/cm2 and fc>250 Hz simultaneously in a single Bi2223 tape. The barrier tape with Lt=4 mm also showed 60%−70% lower perpendicular field losses than a conventional 4 mm-width tape with fully coupled filaments at 10−50 mT and 50 Hz. Although Jc in our barrier tapes is still lower than commercial one, we strongly believe that these achievements are very promising for remarkable improvement for AC performance of Bi2223 tapes in near future. Acknowledgements This work was partially supported by Grant-in-Aids for Scientific Research from MEXT (No. 20686020) and JSPS (No. 22560270) of Japan. It was also supported in part by TEPCO Research Foundation, Research Foundation for the Electrotechnology of Chubu (No. R-20302), DAIKO Foundation, and also by the grant for Young Researchers’ Project of Research Center for Future Technology, Toyohashi University of Technology. The authors would like to thank Messrs. Y. Okumura and T. Makihara in Toyohashi University of Technology for their technical support in all experimental.
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
References [1]
[2]
[3]
AYAI N, KOBAYASHI S, KIKUCHI M, ISHIDA T, FUJIKAMI J, YAMAZAKI K, YAMADE S, TATAMIDANI K, HAYASHI K, SATO K, KITAGUCHI H, KUMAKURA H, OSAMURA K, SHIMOYAMA J, KAMIJYO H, FUKUMOTO Y. Progress in performance of DI-BSCCO family [J]. Physica C, 2008, 468: 1747−1752. KNOOPERS H G, RABBERS J J, TEN HAKEN B, THEN KATE H H J. Magnetization loss in twisted multifilament Bi-2223 tape conductors [J]. Physica C, 2002, 372/376: 1784−1787. FUNAKI K, SASASHIGE Y, YANAGIDA H, YAMASAKI S, IWAKUMA M, AYAI N, ISHIDA T, FUKUMOTO Y, KAMIJO Y. Development of low-AC-loss Bi-2223 superconducting multifilamentary wire [J]. IEEE Trans Appl Supercond, 2009, 19:
[16]
[17] [18]
[19]
3053−3056. MARTÍNEZ E, YANG Y, BEDUZ C, HUANG Y B. Experimental study of loss mechanisms of AgAu/PbBi-2223 tapes with twisted filaments under perpendicular AC magnetic fields at power frequencies [J]. Physica C, 2000, 331: 216−226. KWASNITZA K, CLERK S, FLÜKIGER R, HUANG Y B. Alternating magnetic field losses in high-Tc superconducting multifilament tapes with a mixed matrix of Ag and BaZrO3 [J]. Physica C, 1998, 299: 113−124. DHALLÉ M, POLCARI A, MARTI F, WITZ G, HUANG Y B, FLÜKIGER R, CLERC St, KWASNITZA K. Reduced filament coupling in Bi(2223)/BaZrO3/Ag composite tapes [J]. Physica C, 1998, 310: 127−131. KWASNITZA K, CLERK St, FLÜKIGER R, HUANG Y. Reduction of alternating magnetic field losses in high-Tc multifilament Bi(2223)/Ag tapes by high resistive barriers [J]. Cryogenics, 1999, 39: 829−841. ECKELMANN H, KRELAUS J, NAST R, GOLDACKER W. AC losses in perpendicular external magnetic fields in ring bundle barrier multifilamentary BSCCO(2223) tapes with a central resistive barrier [J]. Physica C, 2001, 355: 278−292. ECKELMANN H, NAST R, SCHMIDT C, GOLDACKER W. Coupling current losses and time constants in multifilamentary BSCCO(2223) tapes with resistive barriers in external magnetic fields [J]. IEEE Trans Appl Supercond, 2001, 11: 2955−2958. NAST R, ECKELMANN H, ZABARA O, SCHLACHTER S, GOLDACKER W. Reduction of coupling current losses by internal resistive barrier structures in multifilamentary Bi(2223) tapes in external magnetic fields [J]. Physica C, 2002, 372/376: 1778−1781. INADA R, NAKAMURA Y, OOTA A, LI C S, ZHANG P X. Fabrication and characterization of Bi2223 tapes with interfilamentary SrZrO3+Bi2212 barriers for AC loss reduction [J]. Supercond Sci Technol, 2009, 22: 035014. INADA R, TATEYAMA K, NAKAMURA Y, OOTA A, LI C S, ZHANG P X. Total AC loss of Ag-sheathed Bi2223 tapes with various filament arrangements carrying AC transport current in AC parallel transverse magnetic field [J]. Supercond Sci Technol, 2007, 20: 138−146. INADA R, OOTA A, LI C S, ZHANG P X. Development of low-loss (Bi,Pb)-2223 tapes with interfilamentary resistive barriers [J]. Adv Sci Technol, 2010, 75: 181−186. MAKIHARA T, INADA R, OOTA A, SAKAMOTO S, LI C S, ZHANG P X. Evaluation of self-field distributions for Bi2223 tapes with oxide barriers carrying DC transport current [J]. IEEE Trans Appl Supercond (to be published). INADA R, TANAKA Y, NAKAMURA Y, OOTA A, LI C S, ZHANG P X. Interfilamentary coupling properties of Bi2223 tapes with resistive silver-alloy sheath in AC perpendicular magnetic field [J]. Abstracts of CSJ Conference, 2009, 81: 4. (in Japanese). TEN HAKEN B, ROBBERS J J, TEN KATE H H J. Magnetization and AC loss in a superconductor with an elliptical cross section and arbitrary aspect ratio [J]. Physica C, 2002, 377: 156−164. CAMPBELL A M. A general treatment of losses in multifilamentary superconductor [J]. Cryogenics, 1982, 22: 3−16. TAKÁCS S, KANEKO H, YAMAMOTO J. Time constants of normal metals and superconductors at different ramp rates during a cycle [J]. Cryogenics, 1994, 34: 679−684. KWASNITZA K, CLERK St. AC losses of superconducting high-Tc multifilament Bi-2223/Ag sheathd tapes in perpendicular magnetic fields [J]. Physica C, 1994, 233: 423−435.
