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F Fukuyama, W B Ali, S Adachi, F Kimura, [N Hirota](https://orcid.org/0000-0001-9189-3673), [T Suzuki](https://orcid.org/0000-0001-9458-6863), [T Uchikoshi](https://orcid.org/0000-0003-3847-4781), S Horii

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[Effect of viscosity of the dispersed media on the bi-axial orientation degrees in magnetically aligned Y123 powder](https://mdr.nims.go.jp/datasets/e2c778a9-80a1-413c-8527-8e59e9608764)

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Journal of Physics:Conference Series      PAPER • OPEN ACCESSEffect of viscosity of the dispersed media on thebi-axial orientation degrees in magnetically alignedY123 powderTo cite this article: F Fukuyama et al 2025 J. Phys.: Conf. Ser. 3054 012013 View the article online for updates and enhancements.You may also likeRecent outreach activities of the EEEProjectC. Ripoli, M. Abbrescia, C. Avanzini et al.-Research on the application of automaticdrilling system for aircraft flap compositetitanium stacked structuresChuanyi Cui, Pin Zhang, Xianglin Gao etal.-Annual quasiperiodicity in muon rateobserved by PolarquEEEst detectors at79°NO. Pinazza, M. Abbrescia, C. Avanzini etal.-This content was downloaded from IP address 144.213.253.16 on 05/12/2025 at 08:37https://doi.org/10.1088/1742-6596/3054/1/012013/article/10.1088/1742-6596/3053/1/012042/article/10.1088/1742-6596/3053/1/012042/article/10.1088/1742-6596/3120/1/012013/article/10.1088/1742-6596/3120/1/012013/article/10.1088/1742-6596/3120/1/012013/article/10.1088/1742-6596/3053/1/012003/article/10.1088/1742-6596/3053/1/012003/article/10.1088/1742-6596/3053/1/012003https://pagead2.googlesyndication.com/pcs/click?xai=AKAOjstKW-k3gf7ozKFGg-o8FpvPkrqz0jzhKIu4SclN23mJpf2z0FCnO0BB40wR0NCp4_Xi0-K47KPyVQgMfJ5Lvx_Fa7pUTnpfLPRnM41mFBSvnpfczvp-ALU9dNc69gIqJ6HKUTc7vlhRwVMJ7cbWefykoywz8CdAeWM0zYHmfK7h0JGlwIbMOIBev-nhUipoEQTG77YpGrQPvnY1faXokO07cspJ0TzLy65G83nD4cVaAIOeZBalMbXPRQBYpfD9bvS9iP7DHOpPDBqDdNr_a-ocFoeFalkCU8S9ZgDLvC-PdSsl3ftH1dleo0T9Ith1NP0d9_z9LwtPOg4ZWAHCDRUM_XVL7Xw1g2awv_WDCCylc3oPr4YWKQa-&sig=Cg0ArKJSzNR7PSH1J-ue&fbs_aeid=%5Bgw_fbsaeid%5D&adurl=https://www.electrochem.org/249%3Futm_source%3DIOP%26utm_medium%3Dbanners%26utm_campaign%3DIOP_249_abstract_submission%26utm_id%3DIOP%2B249%2BAbstract%2BSubmissionContent from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120131 Effect of viscosity of the dispersed media on the bi-axial orientation degrees in magnetically aligned Y123 powder F Fukuyama1*, W B Ali1, S Adachi1, F Kimura1, N Hirota2, T Suzuki2, T Uchikoshi2, and S Horii1 1 Graduate School of Engineering, Kyoto University of Advanced Science, Kyoto, Japan 2 Optical Ceramics Group, National Institute for Materials Science, Tsukuba, Japan  *E-mail: f.fukuyama.ac@gmail.com  Abstract. We clarified the dependence of biaxial orientation degrees on the initial viscosity (ηinit) and curing time (tcure) of resins used for YBa2Cu3Oy (Y123) powder samples aligned under the modulated rotating magnetic fields (MRFs) in two different types of resin. The biaxial orientation degrees of the magnetically aligned Y123 powder samples significantly improved when using a resin with relatively lower ηinit and a longer tcure within the MRF range of 0.8 – 5 T. These findings contribute to the fabrication of rare-earth-based cuprate superconductor ceramics with high biaxial orientation degrees using permanent magnets and the colloidal process.  1. Introduction The cuprate superconductor REBa2Cu3Oy (RE: Rare Earth elements, RE123) with y ~ 7 has a critical temperature (Tc) in the 90 K range [1], which is higher than the boiling point of liquid nitrogen (~ 77 K). Additionally, RE123 exhibits a high critical current density (Jc) under a magnetic field. Its crystal structure of RE123 consists of alternating layers: a one-dimensional CuO-chain as a blocking layer and two-dimensional CuO2 plane as the superconducting layer, oriented along the c-axis. This anisotropic structure results in a strong directional dependence of Jc, where Jc//c < Jc//ab [2]. The short coherence length and d-wave superconducting gap symmetry of the Cooper pair in RE123 lead to serious degradation of the inter-grain Jc. Even in the c-axis aligned bicrystals, the inter-grain Jc at a grain boundary with a misorientation angle of ~ 10 degrees is approximately an order of magnitude lower than the intragranular Jc [3]. To achieve high Jc in both self-field and applied-field conditions, it is essential to form a biaxially aligned grain structure and develop a densified microstructure. Therefore, the fabrication of biaxially aligned RE123 materials currently relies on epitaxial growth techniques, such as thin-film deposition [4] and melt-solidification processes [1].  Magnetic alignment using a modulated rotating magnetic field (MRF) [5-9] is a triaxial grain alignment process for materials with triaxial magnetic anisotropies. A key advantage of this method is that it operates at room temperature. Figure 1 shows a schematic of the intermittent type MRF [8], which is the most common configuration. For a superconducting solenoidal magnet with a room temperature bore [10], the MRF is generated by precisely controlling the rotation of the sample within a static magnetic field (Ba) of up to 10 T level. As shown in Fig. 1, the sample remains stationary at 0° and 180°, while it rotates at intermediate angles. In this setup, the nearly linear static magnetic flux lines inside the superconducting magnet bore are perpendicular to the https://creativecommons.org/licenses/by/4.0/37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120132 α-plane at 0°. The magnetic field’s rotation plane is configured parallel to the γ-plane. Through this process, the first easy and hard magnetization axes align parallel to the static Ba direction and perpendicular to the rotating field plane, respectively. In principle, for a triaxially magnetically aligned sample, the first easy, second easy, and hard magnetization axes are aligned perpendicular to the α-, β-, and γ-planes, respectively. In 2018, our group developed a linear drive-type MRF (LDT-MRF) apparatus for a continuous process triaxial alignment by using a permanent magnet array [11,12]. From the perspective of cost efficiency, LDT-MRF is preferable, as it enables a continuous process and utilizes permanent magnets, significantly reducing the cost of the magnetic alignment process for RE123. However, RE123 must be aligned under a magnetic field of less than 1 T when using permanent magnets. To achieve triaxial magnetic alignment, the magnetic orientation energy must be sufficiently high compared to thermal energy, and the magnetic alignment time (relaxation time, τ) must be significantly shorter than the curing or casting time of the resin or colloidal solution. The value of τ depends on the Ba, triaxial magnetic anisotropy (Δχ), and viscosity (η) of the dispersed medium [13]. In detail, τ is proportional to η and inversely proportional to Δχ and Ba2. Utilizing MRF in combination with the colloidal process is essential for fabricating biaxially aligned RE123 ceramics with improved intergranular connectivity. Generally, the viscosity of colloidal solutions used in this process is 100 - 1000 times lower than that of epoxy resin. Therefore, for practical use, it is crucial to clarify the magnetic alignment behavior in dispersed media with lower η levels (~ 0.01 Pa∙s).  Among RE123 compounds, YBa2Cu3Oy (Y123) is preferred for practical applications due to its relatively lower material cost compared to RE123 with heavy RE ions. However, Y123 has the lowest Δχ in RE123 [14]. Previous studies have shown that biaxial magnetic alignment of Y123 powders in an epoxy resin was not achieved under a 1 T MRF [9], likely because the low Δχ results in an extended τ, which may exceed the curing time of the epoxy resin. Since τ is influenced by η of the dispersed medium, it can be controlled by adjusting η. In the present study, to identify key factors for fabricating magnetically biaxial-aligned Y123 ceramics with high orientation degrees, we investigated the relationship between the dispersed medium and the biaxial orientation degrees of magnetically aligned Y123 powder samples. Biaxial magnetic alignment experiments were conducted on Y123 (y ~ 7) powders under MRFs with varying Ba values in dispersed media with two different initial viscosities (ηinit) and curing times (tcure). The feasibility of magnetically biaxial-aligned Y123 ceramics was evaluated using (103) pole figures at the α-plane.  Figure 1. Schematic of the modulated rotating magnetic field of superconducting magnet (SC-MRF). The first easy, second easy, and hard axes of magnetization are aligned perpendicular to the α-, β-, and γ-planes of the magnetically aligned powder samples, respectively. 37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120133 2. Experimental details Y123 polycrystals were synthesized using a standard solid-state reaction in air. The starting materials, Y2O3, BaCO3, and CuO were weighed in a cationic ratio of Y: Ba: Cu = 1:2:3 and thoroughly ground in ethanol. The mixture was calcined twice at 880 and 900℃, with intermediate grinding. It was then pelletized and sintered at 920℃ for 24 h in air [15]. The obtained Y123 polycrystals were annealed at 300℃ in flowing oxygen gas to achieve y ~ 7, then pulverized in an agate mortar to obtain powders with an average grain size of ~ 5 μm. The pulverized Y123 powders were mixed with epoxy resins at a weight ratio of powder to resin = 1:10 and aligned under MRFs (see Fig. 1) with Ba = 0.8, 1, 3, 5, and 10 T for over 12 h at room temperature. In the present study, the resting time and the rotation speed of MRF were set to be 2 s and 60 rpm, respectively. To determine the biaxial orientation degrees, pole figures of the (103) plane at α-plane were examined on fully cured resins containing the magnetically aligned Y123 powders. The biaxial orientation degree (F) was calculated using the (103) pole figure and the following formula, 𝐹 (%) =𝐼𝑎𝑙𝑖𝑔𝑛𝑒𝑑𝐼𝑎𝑙𝑙× 100                                                                                                                       (1) where Iall is the summation of the intensities in a whole measurement region, and Ialigned is the summation of the intensities at four peaks, including intensities within 5° in radius from the four peaks at Ψ ~ 45°. In principle, perfect biaxial alignment leads to F = 100 %. However, due to the background intensities in realistic pole figure measurements, F does not achieve 100 % even in the perfect biaxial aligned sample. In the present study, F is used as a relative index on the biaxial orientation degrees. 3. Results and discussion Table 1 shows the details of the initial viscosities (ηinit) and the curing times (tcure) for Resin A and B, determined experimentally using viscosities measurement equipment. The initial viscosities of Resin A and B were approximately 40 and 0.5 Pa∙s, respectively. A preliminary study by our group found that the magnetic alignment of Dy123 was achievable even in epoxy resins with ηinit ~ 1000 Pa∙s [16]. Based on this finding, in the present study, the curing time (tcure) of the epoxy resin was conventionally defined as the time at which η reaches 105 Pa∙s. The measured tcure values were approximately 6 h and 10 h for Resin A and B, respectively. In summary, Resin A exhibited a higher ηinit and a shorter tcure than Resin B, while Resin B had a lower ηinit and a longer tcure compared to Resin A. Table 1. Details of the initial viscosities (ηinit) and the curing times (tcure) for Resin A and Resin B. Type of resin Initial viscosity (ηinit) (Pa∙s) Curing time (tcure) (h) Resin A 40 6 Resin B 0.5 10  37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120134  Figures 2(a) and 2(b) show (103) pole figures at α-plane for Y123 powder samples magnetically aligned under a 10 T-MRF in Resin A and Resin B, respectively. Our previous work [14] clarified that the c-axis was the first easy magnetization axis in Y123, and MRFs, it is expected to align perpendicular to the α-plane (see Fig. 1). Therefore, the α-plane is the most appropriate plane for measuring the (103) pole figure. In Fig. 2(a), sharp four-fold symmetric spots were observed at Ψ ~ 45°, resembling the (103) pole figure reported in our previous study [9].  These spots reflect the twin microstructures of Y123 grains, confirming their biaxial alignment under the 10 T-MRF in Resin A. Similarly, in Fig. 2(b), clear four-fold symmetric spots at Ψ ~ 45° indicate that Y123 grains were also biaxially aligned under the 10 T-MRF in Resin B. The calculated biaxial orientation degrees were F ~ 52 % and F ~ 50 % for Resin A and Resin B, respectively. These results suggest that Y123 grains can achieve biaxial alignment under a 10 T-MRF regardless of the initial viscosity of the epoxy resin (ηinit ~ 0.5 Pa·s vs. ηinit ~ 40 Pa·s). This implies that at 10 T, the effects of ηinit and tcure are minimal due to the sufficient magnetic orientation energy and curing time.  Figures 3(a) and 3(b) show the (103) pole figures at the α-plane for Y123 powder samples magnetically aligned under a 1 T-MRF in Resin A and Resin B, respectively. In Fig. 3(a), the (103)  Figure 2. (103) pole figures of magnetically aligned Y123 powder samples with 10 T-MRF in (a) Resin A and (b) Resin B. Ψ and ϕ indicate tilt and rotation angles, respectively.  Figure 3. (103) pole figures of magnetically aligned Y123 powder samples with 1 T-MRF in (a) Resin A and (b) Resin B. Ψ and ϕ indicate the tilt and rotation angles, respectively. 37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120135 pole figure exhibits a circular shape at Ψ ~ 45°, indicating that c-axis grain alignment was achieved in Resin A.  In contrast, Fig. 3(b) shows the four-fold symmetric spots with the broad streaks along the ϕ direction at Ψ ~ 45°, suggesting that Y123 grains with twin microstructures were incompletely biaxially aligned in Resin B. The calculated biaxial orientation degrees were F ~ 13 % and F ~ 23 % for Resin A and Resin B, respectively. These results indicate that under a 1 T-MRF, biaxial orientation degrees can be enhanced by the effects of ηinit and/or tcure. To understand the effects of ηinit and tcure on the biaxial orientation degrees in Y123, Figure 4 presents the relationship between F and Ba for Y123 powder samples aligned in Resin A and Resin B. Note that F includes contributions from both c-axis and in-plane orientation degrees. Focusing on the results for Resin A, the F value showed approximately 12 % at Ba = 0.8 T and was almost unchanged with the increase in Ba up to Ba = 5 T. However, at Ba = 10 T, F significantly improved to approximately 55 %, indicating a remarkable enhancement compared to the range Ba = 0.8 – 5 T. For Resin B, the F values at Ba = 0.8 T and 1 T were approximately 21 % and 23 %, respectively, showing no significant difference. However, at Ba = 3 T, F increased drastically to 42 %, and further improved to approximately 50 % at Ba = 10 T. A common trend observed in Fig. 4 is that the F values improve with increasing Ba, which can be qualitatively explained by the relationship between magnetic orientation energy and Ba. In general, the magnetic orientation energy is proportional to Ba2, leading to enhanced biaxial orientation degrees as Ba increases.  Here, we compare the results for Resin A and Resin B in detail. The most obvious point in Fig. 4 is that the clear differences in the Ba dependence of F between Resin A and Resin B, except at Ba = 10 T. At Ba = 10 T, no clear differences in F were observed between the two resins. However, at Ba = 0.8 T, F for Resin B was higher than that for Resin A. Moreover, for Ba = 3 and 5 T, the differences in F between Resin A and Resin B was more pronounced compared to Ba = 0.8 T. From these experimental results, it was found that Y123 exhibited high biaxial orientation degrees at Ba = 10 T for ηinit ~ 40 Pa∙s, and at Ba > 3 T for ηinit ~ 0.5 Pa∙s. This indicates that F is influenced by the type of epoxy resin. Considering the specifications of Resin A and Resin B in Table 1, it is strongly suggested that lower ηinit and/or longer tcure contribute to higher biaxial orientation degrees in Y123.  As mentioned in Introduction, τ is proportional to η, and inversely proportional to Δχ and Ba2. In principle, the magnetic alignment of grains should be completed before the resin fully cures, meaning τ should be equal to or shorter than tcure. As shown in Table 1, ηinit of Resin A is 80 times higher than that of Resin B, which implies that τ in Resin B is 80 times shorter than that in Resin A. In addition, tcure of Resin B is approximately 1.7 times longer than that of Resin A. Based on this theoretical framework, the nearly constant F values observed at Ba = 10 T can be explained by the fact that τ remains significantly shorter than tcure for both resins. In contrast, for 0.8 T < Ba < 5 T, the obvious differences in F were observed, likely due to the reversal in the relative magnitudes of τ and tcure between Resin A and Resin B. Specifically, in Resin B, τ remains shorter than tcure, facilitating alignment, whereas in Resin A, τ exceeds tcure, limiting alignment. For Y123, which has a relatively low Δχ, achieving sufficiently short τ is crucial under low Ba MRF conditions. A viable approach is selecting a dispersing medium with lower ηinit. As observed in Fig. 4, Y123 showed higher F at Ba = 10 T for ηinit ~ 40 Pa∙s and at Ba > 3 T for ηinit ~ 0.5 Pa∙s. Extrapolating from these results, achieving higher F under lower Ba (e.g., at permanent magnet levels) is expected with a colloidal solution with ηinit < 0.1 Pa∙s. Since the colloidal process is a well-established ceramic fabrication technique, combining MRF at permanent magnet levels with a colloidal process is expected to be a promising method for producing magnetically biaxial aligned Y123 ceramics with high orientation degrees. 37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120136  4. Conclusion In this study, we investigated the biaxial orientation degrees of magnetically aligned Y123 powder samples using Resin A and Resin B. We successfully fabricated the biaxially aligned Y123 under a MRF at a permanent magnet level (Ba ~ 1 T) using Resin B, which has lower ηinit and a longer tcure. The biaxial orientation degrees for Y123, which has the smallest magnetic anisotropy among RE123 compounds, were strongly influenced by ηinit and tcure, in the Ba region of 0.8 T < Ba < 5 T. Our findings suggest that the required Ba for effective magnetic alignment is closely related to the properties of the dispersing media, such as its initial viscosity and casting/curing time. To fabricate the RE-based cuprate superconducting materials using magnetic alignment technique, the combination of magnetic alignment with a colloidal processing approach is essential. Colloidal solution typically has ηinit < 0.1 Pa∙s, leading to significantly shorter τ. If an appropriate casting time is achieved, combining LDT-MRF with a permanent magnet array (Ba ~ 1 T) and a colloidal solution offers a practical route for producing magnetically biaxial aligned Y123 ceramics. References [1] Wu M K, Ashburn J R, Torng C J, Hor P H, Meng R L, Gao L, Huang Z J, Wang Y Q, and Chu C W, “Superconductivity at 93 K in a new mixed-phase Y-Ba-Cu-O compound system at ambient pressure” 1987 Physical Review Letters 58, 908-910. [2]  Yamaki M, Furuta M, Doi T, Shimoyama J, and Horii S, “Fabrication of tri-axially oriented RE-Ba-Cu-O ceramics by magnetic alignment” 2014 Physics Procedia 58, 62-65. [3] Dimos D, Chaudhari P, Mannhart J, and Legoues F K, "Orientation Dependence of Grain-Boundary Critical Currents in YBa2Cu3O7−𝛿 Bicrystals" 1988 Physical Review Letters 61, 219-222.  Figure 4. Ba dependence of F for the magnetically aligned Y123 powder samples with Resin A and Resin B. The applied Ba were 0.8, 1, 3, 5, and 10 T. 37th International Symposium on SuperconductivityJournal of Physics: Conference Series 3054 (2025) 012013IOP Publishingdoi:10.1088/1742-6596/3054/1/0120137 [4] Sawano K, Morita M, Tanaka M, Sasaki T, Kimura K, Takebayashi S, Kimura M, and Miyamoto K, " High Magnetic Flux Trapping by Melt-Grown YBaCuO Superconductors" 1991 Japanese Journal of Applied Physics 30, L1157–L1159. 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[10]  Watanabe K and Awaji S, “Cryogen-Free Superconducting and Hybrid Magnets” 2003 Journal of Low Temperature Physics 133, 17-30. [11] Horii S, Arimoto I, and Doi T, " Linear drive type of modulated rotating magnetic field for a continuous process of three-dimensional crystal orientation " 2018 Journal of the Ceramic Society of Japan 126, 885–888. [12] Ali W B, Adachi S, Kimura F, and Horii S, “Achieving higher orientation degree in DyBa2Cu3Oy (y ∼ 7) superconductor through linear drive type of modulated rotating magnetic field” 2023 Journal of Applied Physics 134, 163901. [13]  Kimura F and Kimura T, “Magnetically textured powders—an alternative to single-crystal and powder X-ray diffraction methods” 2018 CrystEngComm. 20, 861-872. [14] Horii S, Okuhira S, Yamaki M, Kishio K, Shimoyama J, and Doi T, "Tri-axial magnetic anisotropies in RE2Ba4Cu7O15−y superconductors" 2014 Journal of Applied Physics 115, 113908. [15]  Horii S, Fujioka S, and Doi T, “Relationship between biaxial orientation degrees and grain in magnetically aligned (Y1−xErx)Ba2Cu3Oy powders with twin microstructures” 2018 Japanese Journal of Applied Physics 57, 093101. [16] Fukuyama F, Ali B W, Adachi S, Kimura F, and Horii S, “Resin curing time dependence of biaxial magnetic alignment behavior for (Y1-xDyx)Ba2Cu3Oy” The 85th JSAP Autumn Meeting 2024, 17a-C31-8; In the conference, we reported the relationship between resin-curing time and biaxial orientation degrees in epoxy resins with ηinit range from approximately 0.5 Pa∙s to 3000 Pa∙s