# Fileset [Angular_Dependence_of_Critical_Current_and_Grain_Alignment_in_Bi-2223_Superconducting_Joint.pdf](https://mdr.nims.go.jp/filesets/482a9e40-92f5-4afc-a8b7-0d1732e9bb61/download) ## Creator [Yasuaki Takeda](https://orcid.org/0000-0001-7217-9853), [Gen Nishijima](https://orcid.org/0000-0001-7493-0559), Ukyo Nakai, Takanori Motoki, Jun-ichi Shimoyama, [Hitoshi Kitaguchi](https://orcid.org/0000-0002-5998-2649) ## Rights [Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International](https://creativecommons.org/licenses/by-nc-nd/4.0/) ## Other metadata [Angular Dependence of Critical Current and Grain Alignment in Bi-2223 Superconducting Joint](https://mdr.nims.go.jp/datasets/8b63732e-81f7-438b-abd3-2d2f9f960c0d) ## Fulltext Angular Dependence of Critical Current and Grain Alignment in Bi-2223 Superconducting JointIEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 34, NO. 5, AUGUST 2024 6400305Angular Dependence of Critical Current and GrainAlignment in Bi-2223 Superconducting JointYasuaki Takeda , Gen Nishijima , Ukyo Nakai, Takanori Motoki , Jun-ichi Shimoyama ,and Hitoshi KitaguchiAbstract—We clarify the relationship between the angular de-pendence of critical current in a Bi-2223 superconducting jointand the grain alignment of an intermediate layer in the joint. Theangular dependence of critical current for the superconductingjoint is discussed using a model to describe that for a Bi-2223 tape.Considering an angle of the c-axis grain misalignment, the angulardependence is calculated. The misalignment angle is validatedfrom the microstructure observations of the intermediate layer. Wecan conclude that the c-axis grain alignment in the intermediatelayer dominates the angular dependence of critical current in thesuperconducting joint.Index Terms—Bi-2223 tape, critical current, HTS magnets,microscopy.I. INTRODUCTIONSUPERCONDUCTING joints are essential if a supercon-ducting magnet is to be operated in persistent mode [1],[2]. Recently, development of superconducting joints betweenhigh-temperature superconductors (HTSs) has been signifi-cantly progressed [3], [4], [5], [6], [7], [8], [9], [10], [11].We have developed superconducting joints between multifila-mentary (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) tapes [7], [10], [12].An intermediate layer of a polycrystalline Bi-2223 thick filmis used to form a superconducting joint showing high criticalcurrent (Ic).HTS materials show anisotropic electromagnetic properties.One of the properties is observed in Ic of an HTS tape ina magnetic field with various directions, that is, the angulardependence of Ic. It is important to evaluate the angular de-pendence of critical current of a superconducting joint (Icj), asin the case of an HTS tape. This is because in a persistent-modemagnet, a magnetic field with various directions may be appliedto superconducting joints, depending on the magnet design.Evaluation of the angular dependence of Icj for an HTS jointManuscript received 6 October 2023; revised 12 November 2023; accepted 28November 2023. Date of publication 4 December 2023; date of current version14 December 2023. This work was supported in part by JST-Mirai Program underGrant JPMJMI17A2, and in part by JSPS KAKENHI under Grant JP22K14482,Japan (Corresponding author: Yasuaki Takeda.)Yasuaki Takeda, Gen Nishijima, and Hitoshi Kitaguchi are with the NationalInstitute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0003, Japan(e-mail: takeda.yasuaki@nims.go.jp).Ukyo Nakai, Takanori Motoki, and Jun-ichi Shimoyama are with theAoyama Gakuin University, Sagamihara, Kanagawa 230-0045, Japan (e-mail:shimo@phys.aoyama.ac.jp).Color versions of one or more figures in this article are available athttps://doi.org/10.1109/TASC.2023.3338587.Digital Object Identifier 10.1109/TASC.2023.3338587contributes to not only persistent-mode magnet technology butalso materials science of the HTS joints.In a previous study, we evaluated the angular dependence ofIcj for a Bi-2223 closed-loop sample with a superconductingjoint [13]. To evaluate in-field Icj, the decay of a current flowingin the closed loop (Iloop) was measured, while the supercon-ducting joint of the sample was placed in a magnetic field.The direction of the magnetic field was changed by rotating thesample to obtain the angular dependence of Icj. The evaluationof Icj from current decay measurements provides only Icj lowerthan the initial Iloop. The Iloop is introduced into the sample viamagnetic induction using a copper coil located at the center ofthe loop. The initial Iloop is limited by the current of the coppercoil. This is because the temperature of the copper coil, whichis increased due to Joule heating, must be kept sufficiently low.At present, the maximum of the initial Iloop is 220 A. In otherwords, Icj that can be evaluated using this method is up to 220 Aso far.In this study, we discuss the angular dependence of Icj in theBi-2223 superconducting joint. We use a model that describesthe angular dependence of Ic in a Bi-2223 tape consideringan angle of the c-axis grain misalignment in superconductingfilaments [14], [15], [16], [17]. The relationship between theangular dependence of Icj and the grain alignment of an in-termediate layer in the superconducting joint is clarified usingmicrostructure observations.II. EXPERIMENTALA Bi-2223 closed-loop sample with a praying-hands-type su-perconducting joint, which is schematically shown in Fig. 1 andexplained in detail in [10], was prepared. The self-inductance(L) of the sample was 1.4 μH. The sample was made froma commercially available Bi-2223 tape with the Ni-alloy me-chanical reinforcement (DI-BSCCO Type HT-NX, 4.5 mm wideand 0.25 mm thick [18]). The Ic of the tape is about 180 Aat 77 K in self-field and higher than 1 kA at 4 K and 1 Tparallel to the tape surface [19]. Both ends of the tape wereconnected using our joining processes [7], [10], [12], [20].The reinforcement at both ends was removed. To fabricatea superconducting joint, most of the Bi-2223 filaments wereexposed by low-angle polishing at less than 0.5°. The exposedfilaments were connected via an intermediate layer, which wasequivalent to an about 0.1 mm thick polycrystalline Bi-2223film. This thick film was synthesized through the slurry process,© 2023 The Authors. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, seehttps://creativecommons.org/licenses/by-nc-nd/4.0/https://orcid.org/0000-0001-7217-9853https://orcid.org/0000-0001-7493-0559https://orcid.org/0000-0003-3218-0977https://orcid.org/0009-0007-1783-676Xhttps://orcid.org/0000-0002-5998-2649mailto:takeda.yasuaki@nims.go.jpmailto:shimo@phys.aoyama.ac.jphttps://doi.org/10.1109/TASC.2023.33385876400305 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 34, NO. 5, AUGUST 2024Fig. 1. Angular dependence of calculated and experimentally obtained Icjat 4 K and 0.15–0.28 T. Experimentally obtained values are reported in [13].Dashed curves, which are calculated using (1) and (5) with σ= 18.6°, α= 91.7and γ = 0.627, agree well with experimentally obtained values.uniaxial pressing at room temperature, and heat treatments. Theintermediate layer is formed almost parallel to the surface of thetapes at the joint.Icj of the sample at 4 K and 0.15–0.28 T was evaluatedfrom the current decay measurements. Voltage (V) was calcu-lated from time (t) dependence of Iloop using the equation ofV = −L(ΔIloop/Δt). Icj was determined by Iloop at a voltagecriterion (Vc) of 10−8 V in the obtained V–Iloop curve. Byapplying a horizontal magnetic field to the joint and rotatingthe sample incrementally around the vertical axis, we evaluatedthe angular dependence of Icj. Details of the sample fabricationand Icj evaluation, which includes the reason why we chose themagnetic fields of 0.15–0.28 T, are described in [13].We observed the microstructures of the intermediate layer inthe superconducting joint of the sample. The polished surfacesof the transverse cross-sections of the joint were observed. Weused a field emission scanning electron microscope (FE-SEM,Hitachi SU-70) to obtain secondary electron images.III. RESULTS AND DISCUSSIONA. Angular Dependence of Critical Current in Bi-2223Superconducting JointThe experimentally obtained angular dependence of Icj at4 K and 0.15–0.28 T is shown in Fig. 1 [13]. The angle ofthe magnetic field (θ) is determined as schematically shown inFig. 1. θ of 90° corresponds to a magnetic field parallel to thesurface of the tapes at the joint. The experimentally obtainedIcj values increase with increasing the angle. This is similar tothe angular dependence of Ic in a Bi-2223 tape [16], [17]. Asdescribed in Section I, Icj values higher than 220 A at high angleswere not evaluated experimentally.The angular dependence of Icj including at high angles wascalculated using a model that describes the angular dependenceof Ic in a Bi-2223 tape. This model takes the perpendicularcomponent of a magnetic field (B) applied to a tape into accountFig. 2. Icj as a function of perpendicular component of magnetic field calcu-lated using (1) with σ = 18.6°. Experimentally obtained Icj values appear to bescaled. Icj is fitted using (5) with α= 91.7 and γ = 0.627 shown in gray dashedcurve. This curve agrees well with most of experimentally obtained values.as follows [15], [17]:〈B |cos θ|〉 = B∫ 90◦−90◦G (ϕ) |cos (θ + ϕ)| dϕ, (1)where G(ϕ) is a Gaussian distribution of an angle of thec-axis grain misalignment (ϕ) in superconducting filaments andgiven byG (ϕ) =1σ√2πexp(− ϕ22σ2). (2)The standard deviation (σ) is reported to be 6–12° for fila-ments of commercially available Bi-2223 tapes [16], [17], [21].To determine σ, the scaling function off (θ) = 〈B |cos θ|〉 / 〈B |cos (0)|〉 (3)can be used. The relationship between σ and f (90°) ofσ [◦] = 70.9f (90◦) (4)is valid with 1% accuracy in σ ranging from 0 to 20° [15]. Bycomparing the measurement results at θ = 0 and 90°, σ can bedetermined.From current decay measurements at θ= 90°, we experimen-tally obtained the Icj values of 155 and 173 A at 0.70 and 1.0 T,respectively. From the comparison of these Icj values with theIcj values at 0.15–0.28 T and θ = 0, we obtained σ = 18.6°using (4). This σ is larger than the reported values for filamentsof commercially available tapes (6–12°) [16], [17], [21]. Giventhat Icj is mainly dominated by Ic of an intermediate layer [22],the larger σ probably corresponds to the grain misalignment ofthe Bi-2223 intermediate layer in the superconducting joint.Fig. 2 shows Icj as a function of the perpendicular componentof the magnetic field calculated using (1) and σ = 18.6°. Theexperimentally obtained Icj values at 0.15–0.28 T and 0–65°appear to be scaled by , as demonstrated in Bi-2223tapes [15], [16], [17]. This suggests that the model for a tape isapplicable to the superconducting joint.TAKEDA et al.: ANGULAR DEPENDENCE OF CRITICAL CURRENT AND GRAIN ALIGNMENT IN BI-2223 SUPERCONDUCTING JOINT 6400305Fig. 3. (a) Secondary electron image of polished surface of transverse cross-section of intermediate layer of superconducting joint. Grains appeared to beweakly aligned. (b) Magnified view of a grain to indicate how to measure ϕ ofthe grain.Icj shown in Fig. 2 was fitted to the Irie-Yamafuji model, thatis,Icj = α(〈B |cos θ|〉)γ−1, (5)where α and γ are the fitting parameters estimated from theexperimental results [23]. We obtained α= 91.7 and γ = 0.627from the fitting using the least squares method, as shown in thegray dashed curve of Fig. 2. This fitting curve, which agrees wellwith most of the experimentally obtained values, underestimatesthe highest Icj value by 1.79%. An equation considering scalinglaws for the pinning force density may better describe Icj [17].This equation could not be used in this study owing to theinsufficient data on Icj to apply the scaling laws.The calculated angular dependence of Icj at 0.15–0.28 T isshown in dashed curves of Fig. 1. For the calculation, we used (1)and (5) with σ= 18.6°, α= 91.7, and γ = 0.627. The calculatedIcj agrees well with the experimentally obtained values at lowangles. We estimated Icj values at high angles, which were notexperimentally evaluated in the previous study [13]. Consideringthat the model describes well the angular dependence of Ic intapes and reproduces the Icj values at low angles, we believethat the angular dependence of Icj is appropriately describedincluding at high angles.B. Grain Misalignment of Intermediate Layer Evaluated FromMicrostructural ObservationsThe large σ value obtained in the previous section probablycorresponds to the c-axis grain misalignment in the intermediatelayer. To evaluate σ directly, the distribution of the c-axis grainmisalignment angle (ϕ) was examined from the microstructuralobservations of the intermediate layer. Fig. 3(a) shows a sec-ondary electron image of the polished surface of the transversecross-section of the intermediate layer. The horizontal directionis parallel to the tape surface at the joint, corresponding toϕ= 0.Typical plate-like Bi-2223 grains and voids were observed.Many grains showed small ϕ. As reported in [22], the grainsappeared to be weakly c-axis-aligned.Fig. 4. Histogram of misalignment angle ϕ. Three g(ϕ) curves are alsodisplayed. Red solid curve is good agreement with histogram at |ϕ| ≤ 45°.This suggests that at |ϕ| ≤ 45°, ϕ distribution approximately follows Gaussiandistribution with σ = 20.0°.We measured ϕ for each Bi-2223 plate-like grain in threesecondary electron images including Fig. 3(a). The size of eachimage was 13μm× 8.9μm. We measuredϕ for a grain as shownin Fig. 3(b). We drew the straight line along the longitudinaldirection of the grain, which is orthogonal to the direction of thec-axis.ϕ corresponded to the counterclockwise angle formed bythe line and horizontal direction. Theϕ values of all grains in thethree images were measured. In the case of Fig. 3(a), ϕ values of84 grains were measured. The total number of the grains whichwe measured ϕ was 284.Fig. 4 shows a histogram of the misalignment angle ϕ. Theaverage of ϕ (ϕ̄) and standard deviation (σ) were −1.2° and30.9°, respectively. The histogram shows quantitatively that thegrains are weakly aligned, which agrees with the qualitativeimpression obtained from Fig. 3(a).The model to calculate the angular dependence of Icj as-sumes a Gaussian distribution of ϕ. We compared the histogramto the Gaussian distribution described using (2). ϕ̄ was toosmall and neglected. Considering∫ 90◦−90◦ G(ϕ)dϕ ∼= 1, we usedg(ϕ)=NDG(ϕ), where N and D were the sum of the frequenciesand the size of bins (15°), respectively.∫ 90◦−90◦ g(ϕ)dϕ nearlycorresponds to the sum of the area of the bins in the histogram,ND.Three g(ϕ) curves are displayed in Fig. 4. The blue dottedcurve is g(ϕ) with σ = 30.9° and N = 284. This σ was obtainedfrom the distribution over the entire ϕ. The green dashed curveis g(ϕ) with σ = 18.6° and N = 284. This σ corresponds to thatused in the previous section. However, these two g(ϕ) curvesappeared to disagree with the histogram.Hensel et al. proposed the railway-switch model, suggestingthat the small-angle c-axis tilt grain boundaries were the currentpath in filaments of a Bi-2223 tape [24], [25]. Applying thismodel, the grains with large |ϕ| will not contribute to Icj. As-suming that the bins of |ϕ| ≥ 45° can be neglected, ϕ̄ = −0.4°,σ = 20.0°, and N = 242 are obtained. Corresponding g(ϕ) isshown by the red solid curve in Fig. 4. The ϕ̄ was too smalland neglected. This solid curve is in better agreement with the6400305 IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 34, NO. 5, AUGUST 2024histogram at |ϕ| ≤ 45° than the dashed and dotted curves. Thisimplies that at |ϕ|≤ 45°, the distribution of the misalignment an-gleϕ approximately follows the Gaussian distribution describedusing (2) and σ = 20.0°.C. DiscussionIn Section III-A, we used the standard deviation σ of 18.6° tocalculate the angular dependence of Icj. This σ was larger thanthose reported for tapes. In Section III-B, the microstructuralobservations suggested that the distribution of the c-axis grainmisalignment angle ϕ in the intermediate layer follows theGaussian distribution described using (2) and σ = 20.0° at|ϕ| ≤ 45°. This σ is close to the large value of 18.6°. The largeσ used in calculating the angular dependence of Icj is validatedfrom the microstructural observations.The model that describes the angular dependence of Ic of atape [14], [15], [16], [17] assumes a Gaussian distribution of themisalignment angle. As explained in Section III-A, this modelcan also describe the angular dependence of Icj using the largeσ of 18.6°. The microstructural observations of the intermediatelayer validated this large σ and the Gaussian distribution of themisalignment angle. We can conclude that the c-axis grain align-ment in the intermediate layer dominates the angular dependenceof Icj.In the microstructural observations of the intermediate layer,15% of the total grains showed |ϕ|≥ 45°. Because the grains with|ϕ| ≥ 45° will not contribute to the current path, the reduction ofthese grains by improving the grain alignment will be effectiveto increase Icj. In addition, a decrease in σ increases Ic of atape [21]. This also suggests that the improvement of the grainalignment in the intermediate layer to decrease σ is promisingfor increasing Icj.The c-axis grain alignment of a thick film can be improved bymechanical processes using a uniaxial pressure [26]. Uniaxialpressing at a high pressure will be effective to improve the align-ment of an intermediate layer. In this case, mechanical damage ofsuperconducting filaments of joined tapes must be suppressed, asshown in our previous study [22]. An alignment technique usinga magnetic field is also effective for the improvement [27], [28].If the grain alignment of an intermediate layer is improved,higher Icj will be achieved. In contrast, this improvement ofthe grain alignment will also result in the stronger angulardependence of Icj owing to smallerσ. Fig. 5 shows the calculatedangular dependence of Icj at 4 K and 0.15 T. The Icj value isnormalized by that at θ= 0. For the calculation, we used (1) and(5) with σ of 6.0–30.0°, α = 91.7, and γ = 0.627. The blacksolid curve with σ= 18.6° corresponds to the calculated angulardependence of Icj shown in Fig. 1. Inset shows normalized Icjat 90° as a function of σ. At low angles, normalized Icj isindependent on σ. However, normalized Icj at high angles isstrongly dependent onσ. Whenσ decreases from 18.6° to 6.0° (σfor a tape reported in [21]), normalized Icj at 90° increases from1.64 to 2.51. This calculation shows that improvement of thegrain alignment results in the stronger angular dependence of Icj.The stronger angular dependence may not be suitable forapplying superconducting joints to a persistent-mode magnet.Fig. 5. Calculated angular dependence of Icj at 4 K and 0.15 T. Icj values arenormalized by that at θ = 0. Inset shows normalized Icj at 90° as a function ofσ. Improvement of grain alignment results in stronger angular dependence.This is because a magnetic field with various directions maybe applied to the joints, depending on the magnet design. Theangular dependence of Icj should be discussed not only inmaterials science, as in this study, but also in persistent-modemagnet technology.IV. CONCLUSIONThe relationship between the angular dependence of Icj in theBi-2223 superconducting joint and the grain alignment of theintermediate layer was clarified. The angular dependence of Icjwas calculated using the model for a Bi-2223 tape, consideringthe angle of the c-axis grain misalignment. The calculated Icjagreed well with the experimental results. We estimated Icj thatwas not evaluated experimentally. The microstructural observa-tions suggested that the distribution of the misalignment anglein the intermediate layer approximately followed the Gaussiandistribution. The standard deviation of the misalignment angleused in calculating the angular dependence was validated. Weconcluded that the c-axis grain alignment in the intermediatelayer dominated the angular dependence of Icj.The improvement of the grain alignment will result in higherIcj and the stronger angular dependence. The angular depen-dence should be discussed not only in materials science, as inthis study, but also in persistent-mode magnet technology.REFERENCES[1] G. D. Brittles, T. Mousavi, C. R. M. Grovenor, C. Aksoy, and S. C. Speller,“Persistent current joints between technological superconductors,” Super-cond. Sci. Technol., vol. 28, no. 9, Aug. 2015, Art. no. 093001.[2] Y. Takeda, H. Maeda, K. Ohki, and Y. Yanagisawa, “Review of the temporalstability of the magnetic field for ultra-high field superconducting magnetswith a particular focus on superconducting joints between HTS conduc-tors,” Supercond. Sci. Technol., vol. 35, no. 4, Apr. 2022, Art. no. 043002.[3] Y. Park, M. Lee, H. Ann, Y. H. Choi, and H. Lee, “A superconductingjoint for GdBa2Cu3O7−δ-coated conductors,” NPG Asia Mater, vol. 6,May 2014, Art. no. e98.[4] K. Ohki et al., “Fabrication, microstructure and persistent current mea-surement of an intermediate grown superconducting (iGS) joint betweenREBCO-coated conductors,” Supercond. Sci. Technol., vol. 30, no. 11,Oct. 2017, Art. no. 115017.TAKEDA et al.: ANGULAR DEPENDENCE OF CRITICAL CURRENT AND GRAIN ALIGNMENT IN BI-2223 SUPERCONDUCTING JOINT 6400305[5] P. Chen et al., “Development of a persistent superconducting joint be-tween Bi-2212/Ag-alloy multifilamentary round wires,” Supercond. Sci.Technol., vol. 30, no. 2, 2017, Art. no. 025020.[6] S. Mukoyama et al., “Superconducting joint of REBCO wires for MRImagnet,” J. Phys.: Conf. Ser., vol. 1054, 2018, Art. no. 012038.[7] Y. Takeda et al., “High Ic superconducting joint between Bi2223 tapes,”Appl. Phys. Exp., vol. 12, no. 2, Feb. 2019, Art. no. 023003.[8] X. Jin et al., “Superconducting joint between multi-filamentaryBi2Sr2Ca2Cu3O10+δ tapes based on incongruent melting for NMR andMRI applications,” Supercond. Sci. Technol., vol. 32, no. 3, Feb. 2019,Art. no. 035011.[9] T. Mousavi, S. Santra, Z. Melhem, S. Speller, and C. Grovenor, “Su-perconducting joint structures for Bi-2212 wires using a powder-in-tubetechnique,” IEEE Trans. Appl. Supercond., vol. 31, no. 5, Aug. 2021,Art. no. 6400504.[10] Y. Takeda et al., “Critical current improvement and resistance evaluationof superconducting joint between Bi2223 tapes,” Supercond. Sci. Technol.,vol. 35, no. 2, Feb. 2022, Art. no. 02LT02.[11] D. Huang et al., “An efficient approach for superconducting joint of YBCOcoated conductors,” Supercond. Sci. Technol., vol. 35, no. 7, May 2022,Art. no. 075004.[12] Y. Takeda, G. Nishijima, K. Kobayashi, and H. Kitaguchi, “Fabricationof Bi-2223 superconducting joint by hot-pressing process,” IEEE Trans.Appl. Supercond., vol. 33, no. 5, Aug. 2023, Art. no. 6400207.[13] Y. Takeda, G. Nishijima, U. Nakai, T. Motoki, J. Shimoyama, and H.Kitaguchi, “Angular dependence of resistance and critical current of aBi-2223 superconducting joint,” Supercond. Sci. Technol., vol. 36, no. 12,Oct. 2023, Art. no. 125010.[14] L. N. Bulaevskii, L. L. Daemen, M. P. Maley, and J. Y. Coulter, “Limitsto the critical current in high-Tc superconducting tapes,” Phys. Rev. B,vol. 48, no. 18, pp. 13798–13816, Nov. 1993.[15] O. van der Meer, B. ten Haken, and H. H. J. ten Kate, “A model todescribe the angular dependence of the critical current in a Bi-2223/Agsuperconducting tape,” Physica C, vol. 357–360, no. 2, pp. 1174–1177,Aug. 2001.[16] P. Sunwong, J. S. Higgins, and D. P. Hampshire, “Angular, temperature,and strain dependencies of the critical current of DI-BSCCO tapes inhigh magnetic fields,” IEEE Trans. Appl. Supercond., vol. 21, no. 3,pp. 2840–2844, Jun. 2011.[17] D. Kobayashi, T. Okada, and S. Awaji, “High-field critical current proper-ties of (Bi, Pb)2Sr2Ca2Cu3Oy filaments,” IEEE Trans. Appl. Supercond.,vol. 32, no. 4, Jun. 2022, Art. no. 6400105.[18] T. Nakashima et al., “Drastic improvement in mechanical properties ofDI-BSCCO wire with novel lamination material,” IEEE Trans. Appl.Supercond., vol. 25, no. 3, Jun. 2015, Art. no. 6400705.[19] M. Bonura, C. Barth, and C. Senatore, “Electrical and thermo-physicalproperties of Ni-alloy reinforced Bi-2223 conductors,” IEEE Trans. Appl.Supercond., vol. 29, no. 5, Aug. 2019, Art. no. 6400205.[20] Y. Takeda et al., “Development of a persistent current mode 9.39 T (400MHz) LTS/Bi-2223 NMR magnet with a Bi-2223 superconducting joint,”IEEE Trans. Appl. Supercond., vol. 32, no. 6, Sep. 2022, Art. no. 4301005.[21] K. Sato, S. Kobayashi, and T. Nakashima, “Present status and futureperspective of bismuth-based high-temperature superconducting wiresrealizing application systems,” Jpn. J. Appl. Phys., vol. 51, Dec. 2012,Art. no. 010006.[22] Y. Takeda, G. Nishijima, K. Inoue, Y. Takano, and H. Kitaguchi, “Theeffect of intermediate layer densification on the critical current of a Bi-2223superconducting joint,” Supercond. Sci. Technol., vol. 36, no. 3, Jun. 2023,Art. no. 035004.[23] F. Irie and K. Yamafuji, “Theory of flux motion in non-ideal type-II super-conductors,” J. Phys. Soc. Jpn., vol. 23, no. 2, pp. 255–268, Aug. 1976.[24] B. Hensel, J.-C. Grivel, A. Jeremie, A. Perin, A. Pollini, and R. Flükiger,“A model for the critical current in (Bi,Pb)2Sr2Ca2Cu3Ox silver-sheathedtapes: The role of small-angle c-axis grain boundaries and of the texture,”Physica C, vol. 205, no. 3–4, pp. 329–337, Feb. 1993.[25] B. Hensel, G. Grasso, and R. Flükiger, “Limits to the critical trans-port current in superconducting (Bi,Pb)2Sr2Ca2Cu3O10 silver-sheathedtapes: The railway-switch model,” Phys. Rev. B, vol. 51, no. 21,pp. 15456–15473, Jun. 1995.[26] T. Asano, Y. Tanaka, M. Fukutomi, K. Jikihara, J. Machida, and H. Maeda,“Preparation of highly oriented microstructure in the (Bi,Pb)-Sr-Ca-Cu-O sintered oxide superconductor,” Jpn. J. Appl. Phys., vol. 27, no. 9,pp. L1652–L1654, Sep. 1988.[27] S. Horii, R. Nagai, M. Yamaki, T. Maeda, J. Shimoyama, and T. Doi,“Magnetic tri-axial grain alignment achieved in bismuth-based cuprate su-perconductors,” Appl. Phys. Exp., vol. 6, no. 9, Sep. 2013, Art. no. 093102.[28] Y. Takeda, T. Iwami, Y. Saito, T. Motoki, and J. Shimoyama, “Fabricationof high Jc Bi2223 thick films through grain alignment technique using apermanent magnet,” Physica C: Supercond, vol. 584, no. 15, May 2021,Art. no. 1353873.<< /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /None /Binding /Left /CalGrayProfile (Gray Gamma 2.2) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Warning /CompatibilityLevel 1.4 /CompressObjects /Off /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.0000 /ColorConversionStrategy /sRGB /DoThumbnails true /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams true /MaxSubsetPct 100 /Optimize true /OPM 0 /ParseDSCComments false /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveDICMYKValues true /PreserveEPSInfo false /PreserveFlatness true /PreserveHalftoneInfo true /PreserveOPIComments false /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Remove /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true /Algerian /Arial-Black /Arial-BlackItalic /Arial-BoldItalicMT /Arial-BoldMT /Arial-ItalicMT /ArialMT /ArialNarrow /ArialNarrow-Bold /ArialNarrow-BoldItalic /ArialNarrow-Italic /ArialUnicodeMS /BaskOldFace /Batang /Bauhaus93 /BellMT /BellMTBold /BellMTItalic /BerlinSansFB-Bold /BerlinSansFBDemi-Bold /BerlinSansFB-Reg /BernardMT-Condensed /BodoniMTPosterCompressed /BookAntiqua /BookAntiqua-Bold /BookAntiqua-BoldItalic /BookAntiqua-Italic /BookmanOldStyle /BookmanOldStyle-Bold /BookmanOldStyle-BoldItalic /BookmanOldStyle-Italic /BookshelfSymbolSeven /BritannicBold /Broadway /BrushScriptMT /CalifornianFB-Bold /CalifornianFB-Italic /CalifornianFB-Reg /Centaur /Century /CenturyGothic /CenturyGothic-Bold /CenturyGothic-BoldItalic /CenturyGothic-Italic /CenturySchoolbook /CenturySchoolbook-Bold /CenturySchoolbook-BoldItalic /CenturySchoolbook-Italic /Chiller-Regular /ColonnaMT /ComicSansMS /ComicSansMS-Bold /CooperBlack /CourierNewPS-BoldItalicMT /CourierNewPS-BoldMT /CourierNewPS-ItalicMT /CourierNewPSMT /EstrangeloEdessa /FootlightMTLight /FreestyleScript-Regular /Garamond /Garamond-Bold /Garamond-Italic /Georgia /Georgia-Bold /Georgia-BoldItalic /Georgia-Italic /Haettenschweiler /HarlowSolid /Harrington /HighTowerText-Italic /HighTowerText-Reg /Impact /InformalRoman-Regular /Jokerman-Regular /JuiceITC-Regular /KristenITC-Regular /KuenstlerScript-Black /KuenstlerScript-Medium /KuenstlerScript-TwoBold /KunstlerScript /LatinWide /LetterGothicMT /LetterGothicMT-Bold /LetterGothicMT-BoldOblique /LetterGothicMT-Oblique /LucidaBright /LucidaBright-Demi /LucidaBright-DemiItalic /LucidaBright-Italic /LucidaCalligraphy-Italic /LucidaConsole /LucidaFax /LucidaFax-Demi /LucidaFax-DemiItalic /LucidaFax-Italic /LucidaHandwriting-Italic /LucidaSansUnicode /Magneto-Bold /MaturaMTScriptCapitals /MediciScriptLTStd /MicrosoftSansSerif /Mistral /Modern-Regular /MonotypeCorsiva /MS-Mincho /MSReferenceSansSerif /MSReferenceSpecialty /NiagaraEngraved-Reg /NiagaraSolid-Reg /NuptialScript /OldEnglishTextMT /Onyx /PalatinoLinotype-Bold /PalatinoLinotype-BoldItalic /PalatinoLinotype-Italic /PalatinoLinotype-Roman /Parchment-Regular /Playbill /PMingLiU /PoorRichard-Regular /Ravie /ShowcardGothic-Reg /SimSun /SnapITC-Regular /Stencil /SymbolMT /Tahoma /Tahoma-Bold /TempusSansITC /TimesNewRomanMT-ExtraBold /TimesNewRomanMTStd /TimesNewRomanMTStd-Bold /TimesNewRomanMTStd-BoldCond /TimesNewRomanMTStd-BoldIt /TimesNewRomanMTStd-Cond /TimesNewRomanMTStd-CondIt /TimesNewRomanMTStd-Italic /TimesNewRomanPS-BoldItalicMT /TimesNewRomanPS-BoldMT /TimesNewRomanPS-ItalicMT /TimesNewRomanPSMT /Times-Roman /Trebuchet-BoldItalic /TrebuchetMS /TrebuchetMS-Bold /TrebuchetMS-Italic /Verdana /Verdana-Bold /Verdana-BoldItalic /Verdana-Italic /VinerHandITC /Vivaldii /VladimirScript /Webdings /Wingdings2 /Wingdings3 /Wingdings-Regular /ZapfChanceryStd-Demi /ZWAdobeF ] /NeverEmbed [ true ] /AntiAliasColorImages false /CropColorImages true /ColorImageMinResolution 150 /ColorImageMinResolutionPolicy /OK /DownsampleColorImages false /ColorImageDownsampleType /Bicubic /ColorImageResolution 900 /ColorImageDepth -1 /ColorImageMinDownsampleDepth 1 /ColorImageDownsampleThreshold 1.00111 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.76 /HSamples [2 1 1 2] /VSamples [2 1 1 2] >> /ColorImageDict << /QFactor 0.40 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 15 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 15 >> /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 150 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages false /GrayImageDownsampleType /Bicubic /GrayImageResolution 1200 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.00083 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.76 /HSamples [2 1 1 2] /VSamples [2 1 1 2] >> /GrayImageDict << /QFactor 0.40 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 15 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 15 >> /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages false /MonoImageDownsampleType /Bicubic /MonoImageResolution 1600 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.00063 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile (None) /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False /CreateJDFFile false /Description << /CHS /CHT /DAN /DEU /ESP /FRA /ITA (Utilizzare queste impostazioni per creare documenti Adobe PDF adatti per visualizzare e stampare documenti aziendali in modo affidabile. I documenti PDF creati possono essere aperti con Acrobat e Adobe Reader 5.0 e versioni successive.) /JPN /KOR /NLD (Gebruik deze instellingen om Adobe PDF-documenten te maken waarmee zakelijke documenten betrouwbaar kunnen worden weergegeven en afgedrukt. De gemaakte PDF-documenten kunnen worden geopend met Acrobat en Adobe Reader 5.0 en hoger.) /NOR /PTB /SUO /SVE /ENU (Use these settings to create PDFs that match the "Suggested" settings for PDF Specification 4.0) >>>> setdistillerparams<< /HWResolution [600 600] /PageSize [612.000 792.000]>> setpagedevice