Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Takumi Suzuki Last modified date:2019.06.24

Assistant Professor / Measurement and Control Engineering / Department of Electrical Engineering / Faculty of Information Science and Electrical Engineering

1. Y. Onodera, S. Mohan, K. Hisajima, K. Imamura, T. Suzuki, K. Higashikawa, M. Inoue and T. Kiss, Extended current-voltage characteristics in Bi-2223 tape over 7 decades of electric fields including flux creep and flux flow regime, Journal of Physics: Conference Series (2018) in press.
2. K. Higashikawa, T. Suzuki, M. Inoue, S. Fujita, Y. Iijima, T. Kiss, Current Capacity of Cu-Sheathed Multifilamentary Coated Conductors Under the Influence of Spatial Variation of Local Critical Currents in Each Filament, IEEE Transactions on Applied Superconductivity, 10.1109/TASC.2018.2794965, 28, 3, Vol. 28, NO. 3, 4801205, 2018.04.
3. T. Kiss, Masayoshi Inoue, Takumi Suzuki, Lin Lyu, Ken Takasaki, Kazutaka Imamura, Yuta Onodera, Dai Uetsuhara, Akira Ibi, Teruo Izumi, Hitoshi Kitaguchi, Comparison between Bi-2223 tape and RE-123 coated conductor from the view point of current transport properties influencing thermal stability, CRYOGENICS, 10.1016/j.cryogenics.2016.07.004, 80, 221-228, 2016.12, We have investigated flux flow dissipation in typical two kinds of HTS tapes, i.e., a Bi-2223 multi-filamentary tape and a RE-123 coated conductor (CC) from the view point of heat load under over current conditions. Based on systematic measurements on current-voltage characteristics, the nonlinear flux flow dissipation has been described analytically by taking into account current sharing in metallic sheath or stabilization layer. Flux flow dissipation in the RE-123 CC shows much steeper temperature dependence than that of the Bi-2223 tape. As a result, attainable cooling power becomes smaller in the RE-123 CC in comparison with that of Bi-2223 tape even if the same cooling condition. In other word, acceptable temperature rise in the RE-123 CC is small at over current condition, whereas moderate temperature dependence in the Bi-2223 tape allows stable operation even if the bias current exceeds the critical current. Influence of spatial inhomogeneity in the both HTS tapes has also been investigated. Longitudinal variation of local critical current, I-c, and its statistical behavior have been characterized by use of reel-to-reel scanning Hall probe microscopy. It has been found that the flux flow dissipation is possibly localized more than one order higher than that of the average value due to discrete local I-c drops..
4. Satoshi Awaji, Takumi Suzuki, Hidetoshi Oguro, Kazuo Watanabe, Kaname Matsumoto, Strain-controlled critical temperature in REBa2Cu3Oy-coated conductors, scientific reports, 10.1038/srep11156, 5, 11156, 2015.06, Recently, we succeeded in detwinning REBa2Cu3O7 (RE123, RE = rare-earth elements)-coated
conductors by annealing under an external uniaxial strain. Using the untwinned RE123 tapes, the
uniaxial-strain dependencies of the critical temperature Tc along the a and b crystal axes were
investigated over a wide strain region from compression to tension. We found that the strain
dependencies of Tc for the a and b axes obey a power law but exhibit opposite slopes. In particular,
the maximum value of Tc is obtained when the CuO2 plane becomes a square, and its lattice constant
is close to 0.385 nm. It is suggested that a tetragonal structure with a ≈ 0.385 nm is the optimum
condition for a high critical temperature in high-Tc cuprates..
5. Takumi Suzuki, Satoshi Awaji, Hidetoshi Oguro, Kazuo Watanabe, Applied Strain Effect on Superconducting Properties for Detwinned (Y, Gd)BCO Coated Conductors, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2014.2377577, 25, 3, 2015.06, We succeeded in the complete detwin of (Y, Gd) BCO coated conductors using a newly developed in-situ tensile apparatus at high temperature. The intensities of (020) and (200) peaks in a longitudinal and a transverse directions of the tape measured by XRD were similar to each other for usual (Y, Gd) BCO coated conductors before annealing. However, the (200) peak disappears for the longitudinal direction after annealing under the tensile stress. It means that the coated conductors are detwinned by annealing under the tensile stress. We found that T-c linearly decreases with increasing strain for the B-domain (b-axis). This behavior is similar with a uniaxial-pressure effect in (Y, Gd) BCO single crystals. However, the strain dependence of T-c for the A-domain (a-axis) behaves as a power-law function, whereas the uniaxial-pressure dependency of T-c for the a-axis is reported to be linear. In addition, the strain dependencies of J(c) are similar with those of T-c.
6. Satoshi Awaji, Yutaka Yoshida, Takumi Suzuki, Kazuo Watanabe, Kazuyoshi Hikawa, Yusuke Ichino, Teruo Izumi, High-performance irreversibility field and flux pinning force density in BaHfO3-doped GdBa2Cu3Oy tape prepared by pulsed laser deposition, APPLIED PHYSICS EXPRESS, 10.7567/APEX.8.023101, 8, 2, 2015.02, The high irreversibility field B-1 and strong flux pinning force were obtained for BaHfO3-doped GdBa2Cu3Oy tapes on a metallic Hastelloy substrate with an ion beam-assisted deposition MgO buffer layer. At 77.3K, B-1 of 15.8 T and the maximum flux pinning force density of 23.5 GN/m(3) for B parallel to c were achieved for the 1.5 vol % BaHfO3-doped GdBa2Cu3Oy tape, which are the world's highest recorded values for REBa2Cu3Oy-coated conductors on metallic substrates (RE = rare earth). From the flux pinning analysis, the c-axis correlated pinning by well-aligned BaHfO3 nanorods plays an important role in achieving the high irreversibility field and flux pinning force density performance. .
7. Satoshi Awaji, Takumi Suzuki, Hidetoshi Oguro, Kazuo Watanabe, Shutaro Machiya, Michinaka Sugano, Masugu Sato, Tomoyuki Koganezawa, Kaname Matsumoto, Control of residual strain and twin boundary by annealing under strain, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 10.1088/0953-2048/26/6/065013, 26, 6, 2013.06, In REBa2Cu3Oy (RE123, RE = rare earth element) coated conductors, the coexistence of a- and b-axes domains related to a twin structure is one of the origins of the complicated critical current density property and its strain dependence. Hence, control of the twin structure is a very important issue. In the case of Y123 single crystals, detwinning is widely carried out by oxygen annealing under uniaxial stress along the a/b axis. In this study, commercial RE123 superconducting tapes were oxygen-annealed under external strains, similar to the detwinning process of Y123 single crystals. We found that the volume fraction ratio of the a- and b-axis domains changes with the applied external strains during annealing, indicating a change of twin structure. In addition, the residual strains, which are strains induced from the thermal contraction difference between RE123 and the substrate, increase with compression annealing and decrease with tension annealing for RE123 tapes with [100]/[010] orientation along the tape axis. However, those phenomena by strain annealing are not obtained for the [110] oriented RE123 tapes. The strain annealing method that we propose here is very useful to control the internal residual strain and twin structures in an RE123 tape with a [100]/[010] orientation along the tape axis..
8. Takumi Suzuki, Satoshi Awaji, Hidetoshi Oguro, Kazuo Watanabe, Michinaka Sugano, Shutaro Machiya, Masugu Sato, Teruo Izumi, Yuh Shiohara, Improvement of J(c) for GdBCO Coated Conductors by Annealing Under Strain, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 10.1109/TASC.2012.2229376, 23, 3, 2013.06.