春田 正和(ハルタ マサカズ)

産業理工学部 電気電子工学科准教授

Last Updated :2024/06/18

■教員コメント

コメント

エネルギーの有効利用、省エネルギーにつながる電気電子材料・デバイスの開発に取り組んでいます。特に次世代の大容量リチウムイオン電池や全固体電池の実用化を目指しています。

■研究者基本情報

学位

  • 博士(工学)(熊本大学)

研究キーワード

  • エネルギー材料   電気・電子材料   リチウムイオン電池   薄膜   超伝導   

現在の研究分野(キーワード)

エネルギーの有効利用、省エネルギーにつながる電気電子材料・デバイスの開発に取り組んでいます。特に次世代の大容量リチウムイオン電池や全固体電池の実用化を目指しています。

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 電子デバイス、電子機器
  • ナノテク・材料 / エネルギー化学
  • ものづくり技術(機械・電気電子・化学工学) / 電気電子材料工学
  • ナノテク・材料 / 結晶工学
  • ナノテク・材料 / 応用物性

■経歴

経歴

  • 2020年 - 現在  近畿大学産業理工学部准教授
  • 2014年 - 2020年  同志社大学研究開発推進機構准教授
  • 2013年 - 2014年  東北大学原子分子材料科学高等研究機構助手
  • 2010年 - 2013年  高知工科大学 環境理工学群School of Environmental Science and Engineering助教
  • 2007年 - 2010年  産業技術総合研究所エレクトロニクス研究部門産総研特別研究員
  • 2007年 - 2007年  熊本大学ベンチャービジネスラボラトリーポスドク研究員

学歴

  • 2004年04月 - 2007年03月   熊本大学   大学院自然科学研究科   博士後期課程
  • 2002年04月 - 2004年03月   熊本大学   大学院自然科学研究科   博士前期課程
  • 2000年04月 - 2002年03月   熊本大学   工学部   電気システム工学科
  • 1995年04月 - 2000年03月   国立熊本電波工業高等専門学校   電子工学科

委員歴

  • 2016年 - 現在   薄膜材料デバイス研究会   組織委員

■研究活動情報

受賞

  • 2012年 応用物理学会講演奨励賞
     
    受賞者: 春田正和
  • 2006年 低温工学協会九州・西日本支部 支部長賞
     
    受賞者: 春田正和
  • 2005年 電気学会優秀論文発表賞
     
    受賞者: 春田正和
  • 2004年 電気学会支部長賞
     
    受賞者: 春田正和

論文

  • Erika Svensson; Masakazu Haruta; Minoru Inaba; Takayuki Doi
    The Journal of Physical Chemistry C 127 17 7921 - 7928 2023年05月
  • Ryosuke Sugimoto; Kohei Marumoto; Masakazu Haruta; Minoru Inaba; Takayuki Doi
    ChemElectroChem 9 17 2022年09月 [査読有り]
     
    A flat and smooth Li6.6La3Zr1.6Ta0.4O12 (LLZT) pellet was used as a model solid electrolyte to evaluate Li+ transfer resistivity (Ω cm2) at an interface between an LLZT electrolyte and a silicon suboxide (SiOx) electrode. Two types of interfaces were employed; one was a “joint interface” that was formed by depositing a SiOx thin film directly on the LLZT pellet. The other was a “contact interface” that was formed by compressing a SiOx thin film on a Cu foil to the LLZT pellet, which is a more realistic and practicable interface in all-solid-state batteries. The quantitative evaluation of interfacial resistances revealed that Li+ transfer at the solid/solid interfaces was intrinsically more sluggish than that for a solid/liquid one using an electrolyte solution. The interfacial resistivity could be reduced by introducing an artificial solid electrolyte interphase (SEI) to the contact SiOx/LLZT interface.
  • Masakazu Haruta; Hiroto Konaga; Takayuki Doi; Minoru Inaba
    Journal of The Electrochemical Society 169 2 020519 - 020519 2022年01月 [査読有り]
     
    Cycle performance of silicon nano-flake powder (LeafPower® Si) anodes was improved by coating of perfluorosulfonic acid (PFSA) polymers (Nafion® and Aquivion®) as an artificial solid electrolyte interphase (SEI). The Si electrodes were coated with PFSA ionomer by addition of PFSA ionomer solution to aqueous slurry of the Si composite electrode. H+-type Nafion®-coated Si electrodes demonstrated improved capacity retentions and Coulombic efficiencies owing to the formation of a LiF-rich SEI composed of reductive decomposition products of Nafion®. The Nafion® coating suppressed the increase in polarization and the electrode swelling upon cycling because the LiF-rich SEI effectively suppressed electrolyte decomposition. Li+ and Cs+-type Nafion® and H+-type Aquivion®, which has a shorter side chain than Nafion®, provided similar positive effects on cycle performance of the Si electrodes. Furthermore, the Si electrodes achieved good cycleability up to 500 cycles owing to synergy effects of the Nafion® coating and an SEI-forming additive of fluoroethylene carbonate (FEC).
  • Cao, Z.; Haruta, M.; Doi, T.; Inaba, M.
    Journal of the Electrochemical Society 167 4 040508 - 040508 2020年02月 [査読有り]
  • Kei Hosoya; Toshiki Kamidaira; Tetsuya Tsuda; Akihito Imanishi; Masakazu Haruta; Takayuki Doi; Minoru Inaba; Susumu Kuwabata
    Materials Advances 1 4 625 - 631 2020年 [査読有り]
     

    An appropriate combination of Si anodes and binary bis(fluorosulfonyl)amide-based ionic liquid electrolytes significantly improves Li-ion battery performances.

  • Ziyang Cao; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    Journal of the Electrochemical Society 166 16 A4005 - A4013 2019年 [査読有り]
     
    © 2019 The Electrochemical Society. In highly concentrated LiBF4/dimethyl carbonate (DMC) electrolyte, Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) positive-electrode exhibited a good cycle performance and the crack formation in NCM811 particles was remarkably suppressed. However, the high concentration causes some problems, such as a high viscosity, a low ionic conductivity and a high cost. To solve these problems, we chose 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) to dilute the concentrated LiBF4/ and LiPF6/DMC systems. The cycle performance of NCM811 electrode remarkably deteriorated in 0.96 mol kg-1 LiBF4/DMC+HFE (1:2 by volume). Raman spectra indicated that the fraction of freeDMCincreased in the diluted electrolyte, which led to instability against oxidation. However, in the LiPF6/DMC system, the fraction of free DMC had rarely increased after diluted with HFE. The diluted electrolyte showed a high stability against oxidation comparable to the nearly saturated electrolyte, and the NCM811 electrode showed an excellent cycle performance.
  • Masakazu Haruta; Takayuki Doi; Minoru Inaba
    Journal of the Electrochemical Society 166 2 A258 - A263 2019年 [査読有り]
     
    © 2019 The Electrochemical Society. The silicon - oxygen binary system (SiOx) is a promising candidate as a negative electrode for next-generation lithium-ion batteries. Thin SiOx films of different oxygen contents were prepared by magnetron sputtering. Although almost all Si atoms in SiOx at low oxygen contents (x = 0.21 and 0.48) contributed to the reversible alloying/dealloying reactions, an irreversible fraction of Si in SiOx at high oxygen contents (x = 1.09 and 1.78) increased owing to the formation of Li4SiO4. In return for the decrease of reversible capacity, the capacity retention of heavily O-doped SiOx films improved owing to the buffer effect of Li4SiO4 matrix against volume changes. The addition of vinylene carbonate (VC) to the electrolyte further improved the cyclability of the SiOx films, especially those of higher oxygen contents. For the pure-Si film, a sponge-like porous structure appeared after cycling owing to repeated crack formation and inhomogeneous volume changes, and resulted in massive electrode swelling. The morphology change with cycling was suppressed by the presence of Li4SiO4 matrix and a homogeneous solid electrolyte interphase derived from VC, resulting in a superior cycle performance of the heavily O-doped SiOx negative electrodes.
  • Satoshi Hashigami; Kei Yoshimi; Yukihiro Kato; Hiroyuki Yoshida; Toru Inagaki; Masakazu Haruta; Michihiro Hashinokuchi; Takayuki Doi; Minoru Inaba
    ChemistrySelect 4 29 8676 - 8681 2019年 [査読有り]
     
    © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim LiNi0.5Co0.2Mn0.3O2 (NCM) particles coated with lithium boron oxide were prepared by an antisolvent precipitation method. In the antisolvent precipitation method, ethanol was used to strip off the hydrated water coordinated with lithium ions and borate ions. By the antisolvent precipitation method, the NCM particles were coated with a uniform layer of LiBO2. The capacity fading on cycling was successfully suppressed for the lithium boron oxide-coated samples. In addition, the rate capability was also improved by the coating. The lithium boron oxide coating effectively suppressed the increase of the electrode impedance associated with the electrolyte decomposition. Crack formation in the secondary particles after charge-discharge cycling was greatly inhibited for lithium boron oxide-coated NCM. It was demonstrated that the lithium boron oxide coating layer suppressed the side reactions not only on the particle surface, but also in the intergranular cracks by inhibiting the penetration of the electrolyte solution.
  • Takayuki Doi; Ryo Matsumoto; Takatsugu Endo; Ziyang Cao; Taishin Sato; Masakazu Haruta; Michihiro Hashinokuchi; Yoshifumi Kimura; Minoru Inaba
    ACS Applied Energy Materials 2019年 [査読有り]
     
    © 2019 American Chemical Society. A stability against oxidation of ester-based electrolyte solution was highly improved by a tandem preparation method, i.e., increasing concentration of lithium salt and diluting with a miscible diluent. The resultant saturated electrolyte solution offered a wide anodic potential window and allowed a LiNi0.5Mn0.2Co0.3O2 positive electrode to deliver charge/discharge capacities over 200 mAh g-1 up to 4.6 V almost without capacity fading after 50 cycles. The solution structure was studied to clarify the stabilizing mechanism of the electrolyte solution. On the basis of the results, this study presents a viable strategy to design an electrolyte solution with a wide potential window for various electrochemical systems.
  • Yukihiro Kato; Michihiro Hashinokuchi; Satoshi Hashigami; Kei Yoshimi; Hiroyuki Yoshida; Toru Inagaki; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    Journal of the Electrochemical Society 166 6 A941 - A943 2019年 [査読有り]
     
    © 2019 The Electrochemical Society. Lithium silicate was incorporated within Ni0.5CoZMn0.3(OH)2 precursor particles via an anti-solvent precipitation method to prepare lithium silicate-added LiNi0.5Co0.2Mn0.3O2 (NCM) particles. Lithium silicate was found at the grain boundaries in the NCM secondary particles, which significantly improved the capacity retention in high voltage operation (3.0 4.6 V). Cross-sectional SEM images revealed that cracks were seriously formed inside the lithium silicate-free NCM particles after cycling, while crack formation was remarkably inhibited for lithium silicate-added NCM. These results suggested that lithium silicate at the grain boundaries strengthened the interfacial-adhesion between primary particles, resulting in the improved cycling stability.
  • Satoshi Hashigami; Yukihiro Kato; Kei Yoshimi; Akihiro Fukumoto; Ziyang Cao; Hiroyuki Yoshida; Toru Inagaki; Michihiro Hashinokuchi; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    ACS Applied Materials and Interfaces 11 43 39910 - 39920 2019年 [査読有り]
     
    Copyright © 2019 American Chemical Society. The microstructure of LiNi0.8Co0.1Mn0.1O2 cathode materials was controlled by the addition of lithium silicate, and the influence on the cycle performance and the rate capability was investigated. Si was not included within the lattice, but localized at the grain boundaries of the primary particles and the pores inside the secondary particles. The addition of the lithium silicate greatly decreased the density of the pores between the primary particles and improved the density of the secondary particles. The capacity retention was successfully improved for lithium silicate-added LiNi0.8Co0.1Mn0.1O2. When lithium silicate-free LiNi0.8Co0.1Mn0.1O2 was charged to 4.3 V, many cracks were formed along the grain boundaries even in the first cycle, while crack formation was remarkably inhibited for lithium silicate-added LiNi0.8Co0.1Mn0.1O2. Moreover, lithium silicate-added LiNi0.8Co0.1Mn0.1O2 particles were almost free from visible microcracks even after 100 cycles at the discharged state. These results suggest that the lithium silicate reinforces the grain-adhesion at the grain boundaries, inhibiting crack formation and electrolyte decomposition inside the cracks.
  • Masakazu Haruta; Ryuya Hioki; Takashi Moriyasu; Akira Tomita; Toshio Takenaka; Takayuki Doi; Minoru Inaba
    Electrochimica Acta 267 94 - 101 2018年03月 [査読有り]
     
    Silicon flake powder (Si LeafPowder®, Si-LP) with the thickness and lateral dimension of 100 nm and 3–5 μm, respectively, demonstrated superior cycle performance as a negative electrode in lithium-ion batteries. A multi-folded layered structure with many voids was spontaneously formed in Si-LP composite electrodes by morphology changes of Si-LP sheets in repeated charge and discharge cycles. The multi-folded layered structure accommodated volumetric changes of the Si active material and prevented exfoliation of the active material from the current collector, which led to the superior long-term cyclability of the Si-LP electrode. The main factor for capacity fading in long-term cycling was a gradual loss of conduction pathways between Si-LP sheets due to the accumulation of electrolyte reduction products in the electrode. The film-forming additives, vinylene carbonate and fluoroethylene carbonate, effectively suppressed the electrolyte decomposition and remarkably improved the cycle performance of the Si-LP electrode.
  • Haruta, M.; Moriyasu, T.; Tomita, A.; Takenaka, T.; Doi, T.; Inaba, M.
    Journal of the Electrochemical Society 165 9 A1874  2018年 [査読有り]
  • Doi, T.; Matsumoto, R.; Cao, Z.; Haruta, M.; Hashinokuchi, M.; Inaba, M.
    Sustainable Energy and Fuels 2 6 1197  2018年 [査読有り]
  • Minoru Inaba; Masakazu Haruta; Morihiro Saito; Takayuki Doi
    ELECTROCHEMISTRY 85 10 623 - 629 2017年10月 [査読有り]
     
    Silicon is electrochemically alloyed and de-alloyed with Li at potentials close to Li+/Li and is widely recognized as the most promising candidate for the anode of LIBs with a high energy density (250-300 Wh kg(-1)) in the next generation. The most serious issue of Si anode is poor capacity retention owing to large volume changes during charging and discharging. We developed Si LeafPowder (R) with a nano-flake structure to overcome the poor capacity retention. However Si anodes still have some problems such as large irreversible capacity, ceaseless electrolyte decomposition, swelling of the electrode, etc. for use in high-energy density LIBs in the next generation. In this article, these problems and the challenges to mitigate them are overviewed based on our resent data obtained by Si nano-flakes (Si LeafPowder (R)). (C) The Electrochemical Society of Japan, All rights reserved.
  • Shuhei Yoshida; Takashi Okubo; Yuta Masuo; Yasuyuki Oba; Daisuke Shibata; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    ELECTROCHEMISTRY 85 7 403 - 408 2017年07月 [査読有り]
     
    Charge and discharge properties of a graphite/SiOx composite electrode were studied over a wide range of charge/ discharge rates (1/20 to 5C) for use in automotive applications. The graphite/SiOx (90/10 by weight) composite electrode gave a high reversible capacity (453 mAh.g(-1)), and showed a good capacity retention at a low rate of 1/ 20 C. However, the capacity decreased significantly on cycling at a high rate of 2 C. From the analysis of the charging and discharging processes, it was found that the charging reaction occurs predominantly at SiOx particles initially at higher potentials and then proceeds at graphite particles at lower potentials to be fully charged. This tendency was also supported by a dependence of the activation energy of the charge transfer reaction on the state of charge (SOC) estimated by ac impedance analysis. Because the composite electrode contains only 10% SiOx the current was excessively concentrated to the SiOx particles at the initial state when charged at high rates. This caused crack formation in SiOx particles, and the resulting contact loss between particles was considered as the reason for the observed poor cycleability at 2 C. (c) The Electrochemical Society of Japan, All rights reserved.
  • Masakazu Haruta; Takashi Okubo; Yuta Masuo; Shuhei Yoshida; Akira Tomita; Toshio Takenaka; Takayuki Doi; Minoru Inaba
    ELECTROCHIMICA ACTA 224 186 - 193 2017年01月 [査読有り]
     
    Silicon nanoflake powder (Si LeafPowder (R), Si-LP) used as an anode material for lithium-ion batteries has demonstrated superior cycle performance at 30 degrees C in an ethylene-carbonate-based electrolyte solution because its characteristic thin-film-based structure resists pulverization. However, capacity fading was accelerated at 60 degrees C owing to enhanced decomposition of the electrolyte solution and growth of a solid electrolyte interface (SEI), which leads to loss of the electronic contact between Si-LP particles. The SEI-forming additives vinylene carbonate (VC), fluoroethylene carbonate (FEC), and difluoroethylene carbonate improved the capacity retention and Coulombic efficiency at 30 degrees C. Although VC is the most effective additive at 60 degrees C, the discharge capacity was decreased dramatically at - 5 degrees C owing to poor ionic and electronic conductivity of the SEI layer formed from the VC-added electrolyte solution. The added FEC produced better performance in a wide temperature range of - 5 to 60 degrees C because the SEI layer formed in the FEC-added electrolyte solution had higher ionic and electronic conductivity than that formed from VC, even at - 5 degrees C. To obtain Si anodes with high discharge capacity and long cycle life, an appropriate choice of SEI-forming additive taking into account the operating temperature is important. (C) 2016 Elsevier Ltd. All rights reserved.
  • Shuhei Yoshida; Yuta Masuo; Daisuke Shibata; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 164 1 A6084 - A6087 2017年 [査読有り]
     
    The amounts of adsorbed water on several kinds of carbon and silicon materials including Si nano-flake powder (Si LeafPowder, Si-LP) were determined at 250 degrees C. It was found that nano-sized Si materials adsorb a large amount of water even after being dried at 120 degrees C because of the hydrophilicity of the surface and the high specific surface area. The adsorbedwater on Si-LP can be removed, but not completely, after drying at a 180 degrees C. The charge and discharge characteristics of Si-LP, especially the initial irreversible capacity and the coulombic efficiencies upon repeated cycling, were significantly improved by removal of the adsorbed water at 180 degrees C. The 180 degrees C-dried sample also suppressed gas evolution during the initial charging and discharging cycle. From the results of gas analysis, it was found that gases evolved from the Si-LP electrodes were mainly H-2 and CO2. From the results of charge and discharge tests and gas analysis, the effect of the adsorbed water on the irreversible decomposition of the electrolyte solution was discussed. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.
  • Zhe Li; Yutaro Kamei; Masakazu Haruta; Toshio Takenaka; Akira Tomita; Takayuki Doi; Shiguo Zhang; Kaoru Dokko; Minoru Inaba; Masayoshi Watanabe
    ELECTROCHEMISTRY 84 11 887 - 890 2016年11月 [査読有り]
     
    A lithium-sulfur cell was developed, consisting of a Si nanoflake negative electrode, a Li2S/graphene positive electrode, and a non-flammable solvate ionic liquid electrolyte. This cell configuration allows us to avoid the use of Li metal electrode and the concomitant dendritic deposition of Li metal at the negative electrode during charging, thereby rendering the cell operation highly safe and stable. The solvate ionic liquid electrolyte solution was composed of tetraglyme, lithium bis(trifluoromethanesulfonyl)amide, and a hydrofluoroether. The solubility of lithium polysulfide (reaction intermediate of the positive electrode) is very low, resulting in high Coulombic efficiency of discharge/charge and long cycle life of the Si/Li2S cell. (C) The Electrochemical Society of Japan, All rights reserved.
  • Chih-Yao Chen; Teruki Sano; Tetsuya Tsuda; Koichi Ui; Yoshifumi Oshima; Masaki Yamagata; Masashi Ishikawa; Masakazu Haruta; Takayuki Doi; Minoru Inaba; Susumu Kuwabata
    SCIENTIFIC REPORTS 6 2016年10月 [査読有り]
     
    A comprehensive understanding of the charge/discharge behaviour of high-capacity anode active materials, e.g., Si and Li, is essential for the design and development of next-generation high-performance Li-based batteries. Here, we demonstrate the in situ scanning electron microscopy (in situ SEM) of Si anodes in a configuration analogous to actual lithium-ion batteries (LIBs) with an ionic liquid (IL) that is expected to be a functional LIB electrolyte in the future. We discovered that variations in the morphology of Si active materials during charge/discharge processes is strongly dependent on their size and shape. Even the diffusion of atomic Li into Si materials can be visualized using a back-scattering electron imaging technique. The electrode reactions were successfully recorded as video clips. This in situ SEM technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data.
  • Masakazu Haruta; Susumu Shiraki; Takeo Ohsawa; Tohru Suzuki; Akichika Kumatani; Yoshitaka Takagi; Ryota Shimizu; Taro Hitosugi
    SOLID STATE IONICS 285 118 - 121 2016年02月 [査読有り]
     
    An all-in-vacuum (in-vacuo) fabrication and evaluation system for thin-film all-solid-state lithium batteries was designed and constructed. To prepare clean solid electrolyte/electrode interfaces, ultra-high-vacuum (UHV) chambers for the deposition of cathode, electrolyte, and anode thin films were directly connected to each other. Thus, throughout the fabrication and evaluation, the samples were maintained under UHV conditions, not exposed to air. The thin-film lithium battery, with a clean and well-defined solid electrolyte/electrode interface, exhibited very good electrochemical properties even without post-deposition annealing. This performance is attributed to the clean solid electrolyte/electrode interface prepared in the vacuum. (C) 2015 Elsevier B.V. All rights reserved.
  • Susumu Shiraki; Yoshitaka Takagi; Ryota Shimizu; Tohru Suzuki; Masakazu Haruta; Yukio Sato; Yuichi Ikuhara; Taro Hitosugi
    THIN SOLID FILMS 600 175 - 178 2016年02月 [査読有り]
     
    We demonstrate the deposition of LiCoO2(11-20) epitaxial thin films on chemically etched Pt(110) substrates, and compare their electrochemical properties with those of LiCoO2(10-14) epitaxial thin films on sputter-annealed Pt(110) reconstructed substrates. Cyclic voltammogram measurements of LiCoO2(11-20) epitaxial films exhibit stable charge and discharge operations, despite the application of a compressive strain on the films. (C) 2016 Elsevier B.V. All rights reserved.
  • Ryotaro Kanazawa; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    ELECTROCHEMISTRY 83 10 867 - 869 2015年10月 [査読有り]
     
    Carbon-modified ramsdellite titanium dioxide, TiO2(R), was prepared without using metallic Ti powder, and its charge and discharge properties was investigated as an anode of lithium ion batteries. Carbon sources (citric acid and multi-walled carbon nanotubes) were added in the calcination process to obtain a LiTi2O4 precursor. The carbon addition was indispensable to obtain stoichiometric LiTi2O4 as a precursor and the resulting Li+-free TiO2(R). The carbon-modified TiO2(R) had a round shape and a smaller particle size of 0.5-1.5 mu m. The discharge capacity and rate-capability were improved by carbon modification due to an enhancement of the electronic conductivity and a reduction of the lithium-ion diffusion path. (C) The Electrochemical Society of Japan, All rights reserved.
  • Shuhei Yoshida; Yuta Masuo; Daisuke Shibata; Masakazu Haruta; Takayuki Doi; Minoru Inaba
    ELECTROCHEMISTRY 83 10 843 - 845 2015年10月 [査読有り]
     
    To compensate a large initial irreversible capacity (Q(irr)) of silicon electrode, a novel Li pre-doping technique using Li-naphthalene complex/tetrahydrofuran solutions was developed. Li was successfully doped to amorphous silicon nano-flake particles, and the doping level of Li was easily controlled by adjusting naphthalene concentration. A large Q(irr) of the pristine electrode (1200 mAh g(-1)) was almost completely compensated after pre-doped in 0.1 mol dm(-3) Li-naphthalene solution for 1 h. In addition, no harmful effects of pre-doping on cycleability were observed. (C) The Electrochemical Society of Japan, All rights reserved.
  • Shigeru Horii; Masakazu Haruta; Ataru Ichinose; Toshiya Doi
    JOURNAL OF APPLIED PHYSICS 118 13 2015年10月 [査読有り]
     
    We report the dependence of critical temperature (T-c), the irreversibility line, the microstructure of nanorods with perovskite-based barium niobates (BNOs), and the c-axis length of the YBa(2)Cu(3)Oy (Y123) superconducting matrix on the BNO-doping level and growth temperature for Y123 thin films with BNO nanorods. The characteristic field (B-cr) determined from the vortex-Bose-glass-like irreversibility lines in Y123+BNO films is strongly correlated to the BNO nanorod density and the growth temperature. Despite a monotonic decrease in T-c with increasing B-cr and nanorod density, the irreversibility fields (B-irr) were enhanced up to B-cr similar to 5 T. From the B-cr value and the mean diameter of the BNO nanorod (similar to 10 nm), we estimate that a lower T-c matrix annulus with a diameter of 12-14 nm exists around each BNO nanorod due to the strong interface strains. Our present study suggests that generation of this lower T-c region around each BNO nanorod increases the vortexpinning strength significantly and, moreover, may offer a new way of enhancing B-irr for REBa2Cu3Oy film with nanorods. (C) 2015 AIP Publishing LLC.
  • Masakazu Haruta; Yuta Masuo; Takashi Moriyasu; Akira Tomita; Chihiro Sakakibara; Akika Kamei; Masato Hirota; Toshio Takenaka; Takayuki Doi; Minoru Inaba
    ELECTROCHEMISTRY 83 10 837 - 839 2015年10月 [査読有り]
     
    Charge and discharge properties of amorphous Si nano-flake powder (Si Leaf Powder (R), Si-LP) in lithium bis(trifluoromethanesulfonyl)amide-tetraglyme complex electrolyte, [Li(G4)][TFSA], were investigated for use as an anode in silicon-sulfur battery. Though a high reversible capacity (2,300-2,700 mAh g(-1)) was obtained initially in [Li(G4)][TFSA], the overpotential gradually increased upon cycling. The increase in overpotential was reduced by dilution with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The addition of fluoroethylene carbonate (FEC) further reduced the overpotential and improved cycleability. Electrochemical impedance spectroscopy analysis revealed that the observed improvements in charge and discharge characteristics are due to the formation of solid electrolyte interface layer with a high ionic-conductivity in the presence of FEC. (C) The Electrochemical Society of Japan, All rights reserved.
  • Masakazu Haruta; Susumu Shiraki; Tohru Suzuki; Akichika Kumatani; Takeo Ohsawa; Yoshitaka Takagi; Ryota Shimizu; Taro Hitosugi
    NANO LETTERS 15 3 1498 - 1502 2015年03月 [査読有り]
     
    In this paper, we report the surprisingly low electrolyte/electrode interface resistance of 8.6 Omega cm(2) observed in thin-film batteries. This value is an order of magnitude smaller than that presented in previous reports on all-solid-state lithium batteries. The value is also smaller than that found in a liquid electrolyte-based batteries. The low interface resistance indicates that the negative space-charge layer effects at the Li3PO4-xNx/LiCoO2 interface are negligible and demonstrates that it is possible to fabricate all-solid state batteries with faster charging/discharging properties.
  • Susumu Shiraki; Hideki Oki; Yoshitaka Takagi; Tohru Suzuki; Akichika Kumatani; Ryota Shimizu; Masakazu Haruta; Takeo Ohsawa; Yukio Sato; Yuichi Ikuhara; Taro Hitosugi
    JOURNAL OF POWER SOURCES 267 881 - 887 2014年12月 [査読有り]
     
    We demonstrate the orientation control of LiCoO2 epitaxial thin films deposited on (110)-2 x 1 reconstructed surfaces of Au and Pt by using pulsed laser deposition. The epitaxial LiCoO2 thin films have CoO2 layers tilted with respect to the surface normal, which is suitable for Li-ion insertion/extraction reactions in LiCoO2. We show the successful operation of all-solid-state thin-film Li-ion batteries by employing the epitaxial LiCoO2 thin films as cathodes. The electrochemical properties of epitaxial films in all-solid-state batteries are improved compared to the batteries using liquid electrolyte. (C) 2014 Elsevier B.V. All rights reserved.
  • Shigeru Horii; Momoko Yamaki; Masakazu Haruta; Jun-Ichi Shimoyama
    ELECTRONICS AND COMMUNICATIONS IN JAPAN 97 4 10 - 18 2014年04月 [査読有り]
     
    We report changes in the degree of triaxial orientation as functions of the applied magnetic field and rotation rate for Y2Ba4Cu7Oy powder samples oriented in epoxy resin under modulated rotating magnetic fields (MRFs). Although the degrees of orientation were reduced as a result of a decrease in both the applied field and rotation rate, the mechanisms of the reduction of the degrees of orientation were found to be different. Optimization of the MRF conditions or quantification of triaxial magnetic anisotropy in a target substance is required for the production of triaxially oriented ceramics based on a colloidal process.
  • R. Nagai; S. Horii; T. Maeda; M. Haruta; J. Shimoyama
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 494 50 - 53 2013年11月 [査読有り]
     
    We report relationship between the degrees of tri-axial orientation and doping level of rare earth (RE) ions in Bi2Sr2(Ca1 xREx)Cu2Oy (RE-doped Bi2212; RE = Dy, Ho, Er and Tm) powder samples aligned under a modulated rotation magnetic field (MRF) of 10 T. Tri-axial magnetic alignment of the RE-doped Bi2212 with x = 0-0.5 was achieved by single-ion magnetic anisotropy of RE3+ and tri-axial magnetic anisotropy induced by modulation microstructure in a grain level. The degrees of in-plane and c-axis orientation with similar to 3 degrees were achieved for the case of the Tm-doped Bi2212 with x = 0.5. The findings in the present study give us important information for the fabrication of triaxially oriented Bi-based cuprate superconductor materials by the magneto-scientific process. (C) 2013 Elsevier B.V. All rights reserved.
  • T. Ugawa; S. Horii; T. Maeda; M. Haruta; J. Shimoyama
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 494 41 - 45 2013年11月 [査読有り]
     
    We report magnetic alignment of YBa2(Cu-1 Fe-x(x))(3)O-y (Fe-doped Y123, x = 0-0.1) powders under modulated rotation magnetic fields (MRFs) and roles of Fe ion as a determination factor of magnetic anisotropy in Y123. The Fe-free and Fe-doped Y123 powder samples aligned in the MRF of 10 T showed two different orientation types of the hard axis in Y123 grains. From an X-ray rocking curve measurement for the magnetically aligned powder samples of the Fe-doped Y123, inplane magnetic anisotropy for Y123 grains with the hard axis parallel to the [110] direction was found to be higher than that for Y123 grains with the hard axis parallel to the [010] direction. (C) 2013 Elsevier B.V. All rights reserved.
  • N. Fujita; M. Haruta; A. Ichinose; T. Maeda; S. Horii
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 494 140 - 143 2013年11月 [査読有り]
     
    The vortex-Bose-glass-like irreversibility lines (ILs) emerged for 2.5 and 5.0 at.% Ba-Nb-O (BNO)-doped YBa2Cu3Oy films deposited by PLD using Nd:YAG-laser. The ILs strongly depended on growth temperature (T-s) in addition to the doping level of BNO. The vortex glass region was expanded with increasing T-s or doping level of BNO. Drastic change of the nanorod morphology from short and bended nanorods to long and linear nanorods with increasing T-s was clarified. Moreover, it was found that T-s-dependent ILs were quite different from our previous results in BNO-doped ErBa2Cu3Oy films. (C) 2013 Elsevier B. V. All rights reserved.
  • S. Horii; T. Ugawa; M. Haruta; A. Ishihara; J. Shimoyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 2013年06月 [査読有り]
     
    The effects of doping of the cobalt ion on magnetic anisotropy in twinned and orthorhombic YBa2Cu3Oy (Y123) were clarified from their magnetic alignment behaviors under a modulated rotating field of 10 T. The cobalt-free Y123 shows two different types of inplane orientation due to the twin microstructure, and the cobalt-doping induced a structural change into a tetragonal phase and conversion of the magnetic hard axis from the b-axis ([100] grain) into a [110] direction ([110] grain). Furthermore, magnetic alignment under a modulated rotating field of 5 T revealed that the inplane magnetic anisotropy of the [110] grains is superior to that of the [100] grain. It is likely that crystallochemical control at the chain site in Y123 promotes the bi-axial orientation using the [110] grains as a grain alignment type for the bi-axial magnetic alignment of twined Y123.
  • M. Haruta; A. Ichinose; N. Fujita; K. Saura; T. Maeda; S. Horii
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 2013年06月 [査読有り]
     
    Growth temperature (T-s) dependent microstructures of nanorods were clarified for BaNb2O6 (BNO)-doped YBa2Cu3Oy (Y123) films. The morphology of BNO in the Y123 matrix was changed from fluctuated nanorods to uniform nanorods with the increase in T-s. Reflecting this change in the nanorod morphology, spatial distribution of local critical current density (J(cl)) determined from the percolation transition model became sharp with the increase in T-s. The sharp distribution of J(cl) led to a steep slope of electric field vs. current density curve and a sharp J(c) peak under B//c in the magnetic field angular dependence. The evaluation of the distribution of J(cl) is a strong tool to understand quantitatively the relationship between the microstructure of nanorods and critical current properties for RE123 films with nanorods. To optimize the critical current properties under the magnetic field for RE123 coated conductors with nanorods, precise control of T-s is very important in the production process.
  • Relationship between critical current properties and nanorod morphology in REBa2Cu3Oy thin films
    M. Haruta; N. Fujita; Y. Ogura; T. Nakata; T. Maeda; A. Iichinose; P. Mele; K. Matsumoto; S. Horii
    Mat. Res. Soc. Symp. Proc. 1434 1588 - 1593 2013年 [査読有り]
  • Relationship between grain size and the degrees of orientation in a twinned ErBa2Cu3Oy superconductor oriented in modulated rotating magnetic fields
    S. Horii; S. Okuhira; M. Yamaki; M. Haruta; J. Shimoyama
    Mat. Res. Soc. Symp. Proc. 1434 918 - 923 2013年 [査読有り]
  • Masakazu Haruta; Keisuke Saura; Natsuto Fujita; Yuta Ogura; Ataru Ichinose; Toshihiko Maeda; Shigeru Horii
    Physica C: Superconductivity and its Applications 494 158 - 162 2013年 [査読有り]
     
    In-field Jcs were improved by introducing Ba-Nb-O (BNO)-nanorods in YBa2Cu3Oy (Y123) and ErBa 2Cu3Oy (Er123) films. Retention of J c against the magnetic field for the BNO-doped Er123 film was superior to that for the BNO-doped Y123 film. Sharp distribution of local critical current density originating from vortex pinning by nanorods with uniform morphology was demonstrated in the Er123 film. On the other hand, fluctuating microstructures of nanorods formed in the Y123 film prepared by the same deposition conditions. Moreover, different growth temperature dependences of nanorod morphology between the Y123 and Er123 films were clarified. © 2013 Elsevier B.V. All rights reserved.
  • Shigeru Horii; Natsuki Okamoto; Keisuke Aoki; Masakazu Haruta; Jun-ichi Shimoyama; Kohji Kishio
    JOURNAL OF APPLIED PHYSICS 112 4 2012年08月 [査読有り]
     
    The tri-axial grain alignment of thermoelectric Bi-based cobaltites with a misfit-layered structure by a modulated rotation magnetic field (MRF) of 10 tesla (T) was demonstrated. To maximize the degrees of tri-axial grain alignment in [ (Bi2-xPbx)(AE(2-y)RE(y))O-4](p)CoO2 powder samples aligned under the MRF of 10 T, the following three crystallochemical approaches are important: doping of Pb into the Bi site, appropriate choice of an alkali earth (AE) ion, and doping of the appropriate rare earth (RE) ion into an AE site. Namely, simultaneous introduction of the relaxation effect of the misfit structure, creation of a domain structure with shear-type discontinuity, and single-ion magnetic anisotropy, which are induced by doping of Pb, Sr, and RE (Pr and Nd), respectively, into the Bi-based cobaltite achieved high degrees of tri-axial grain alignment below 4 degrees. The present study provides a crystallochemical strategy for the fabrication of grain-aligned ceramics of misfit-layered Bi-based cobaltites with high thermoelectric performance by the magneto-scientific technique using MRF. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747940]
  • Masakazu Haruta; Ataru Ichinose; Natsuto Fujita; Yuta Ogura; Takahiro Nakata; Toshihiko Maeda; Shigeru Horii
    APPLIED PHYSICS EXPRESS 5 7 2012年07月 [査読有り]
     
    Uniform irreversibility lines (ILs) and the morphology of nanorods independent of the growth temperature (T-s) were demonstrated by controlling the chemical compositions in superconducting REBa2Cu3Oy (RE123) matrix. Tailoring the composition ratios of Y and Er in an RE123 matrix using Ba-Nb-O-doped Y123 and Er123 films with opposite T-s-dependent ILs, almost constant ILs with a matching field of similar to 4 T, and linear growth of nanorods were achieved in a wide T-s region of 40 degrees C (T-s = 850-890 degrees C). The present study provides a novel strategy for the doping of nanorods in RE123-coated conductors with spatially uniform and high in-field critical current properties. (C) 2012 The Japan Society of Applied Physics
  • T. Tashiro; T. Maeda; R. Abe; S. Takechi; T. Takahashi; M. Haruta; S. Horii
    ADVANCES IN SUPERCONDUCTIVITY XXIV 27 21 - 23 2012年 [査読有り]
     
    One of related materials to high-temperature superconductors (HTSC's) with nominal compositions of (Pb0.5Co0.5)Sr-2(Y1-xCax) Cu(2)Oz (x=0 similar to 0.6) is synthesized and characterized. All samples are nearly single-phase, and its crystal structure is likely to be so-called '' 1-2-1-2 '' type which is one of typical structures of HTSC's. Electrical resistivity is decreased as x increases. While superconductivity is not observed at temperatures between room-temperature and 20 K for all samples, temperature dependence of the resistivity exhibits metallic behavior down to 150 K for x=0.5. Phase formation and transport behavior are discussed focusing on mixed valence-state of Co2+ and Co3+. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of ISS Program Committee.
  • M. Yamaki; S. Horii; M. Haruta; J. Shimoyama
    ADVANCES IN SUPERCONDUCTIVITY XXIV 27 136 - 139 2012年 [査読有り]
     
    We report an effect of rotation speed (Omega) on the degrees of orientation of three different crystallographic axes for Y2Ba4Cu7Oy powders oriented under modulated rotation magnetic fields (MRFs) of 10 T. The degrees of inplane and c-axis orientations below 4 degrees were achieved for the MRFs with Omega >= 10 rpm in 10 T. The hard magnetic axis, the b-axis, of Y247 was highly oriented even for the lowest rotation speed, Omega = 1 rpm, within the present study. However, the degrees of orientations of the first and secondary easy axes, were drastically reduced for Omega < 10 rpm. The present study revealed that, under the MRF of 10 T, the decrease in Omega induced the following of the first easy axis synchronized with by the rotation of magnetic fields, and gives us important information for the fabrication of tri-axially oriented RE-based cuprate superconductors by the magneto-scientific process using MRF. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of ISS Program Committee
  • Masakazu Haruta; Natsuto Fujita; Toshihiko Maeda; Shigeru Horii
    SUPERCONDUCTIVITY CENTENNIAL CONFERENCE 2011 36 1576 - 1581 2012年 [査読有り]
     
    Bi-axially oriented YBCO thin films with BNO-nanorods were obtained by a low cost PLD process using Nd:YAG-laser in the substrate temperature (T-s) range of 850-890 degrees C, and the degrees of orientation for the films are comparable to those of YBCO films prepared by PLD with excimer-laser. The vortex-Bose-glass-like behavior of irreversibility lines emerged and strongly depended on T-s in the YBCO films with BNO-nanorods. Dependence of J(c) on the magnetic field was improved by introduction of BNO-nanorods, whereas J(c) properties were sensitively affected by T-s. Control of T-s is an important factor for the production of high-performance REBCO coated conductors with nanorods. (C) 2012 Published by Elsevier B. V. Selection and/or peer-review under responsibility of the Guest Editors.
  • Shigeru Horii; Natsuto Fujita; Yuta Ogura; Toshihiko Maeda; Masakazu Haruta
    ADVANCES IN SUPERCONDUCTIVITY XXIV 27 220 - 223 2012年 [査読有り]
     
    We report optimization of substrate temperature (T-s) regions for achievement of the bi-axially oriented growth without the a-axis oriented domains, critical current properties and crystallinities in REBa2Cu3Oy (RE123) films (RE= Y and Er) grown by pulsed laser deposition using a Nd:YAG laser. Appropriate T-s regions for achieving both high critical temperature and self-field critical current density in Y123 and Er123 films were found to be similar. In the case of Y123, infield critical current densities and inplane lattice parameters for the Y123 films grown in a lower T-s region were slightly changed compared with those for the films grown at a higher T-s region. Our findings in the present study give us fundamental information to understand intrinsic effects of introduction of nanorods in the RE123 films containing nanorods. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of ISS Program Committee.
  • K. Aoki; S. Horii; M. Haruta; H. Ogino; J. Shimoyama
    ADVANCES IN SUPERCONDUCTIVITY XXIV 27 164 - 167 2012年 [査読有り]
     
    From magnetic orientation under static and rotating magnetic fields for REOFeAs, REOCuS and FeCh, we discuss determination factors of magnetic anisotropies for the above compounds. Behaviours of the magnetic orientation were quite different between REOFeAs and REOCuS, and revealed that FeAs layers and RE3+ ions played main roles as determination factors of magnetic anisotropies in REOFeAs and REOCuS, respectively. Furthermore, FeSe and FeTe compounds with the same crystal structure possess different magnetic axes, and we clarified that FeTe was the one and only compound with the easy axis parallel to the c-axis among the Fe-based layered compounds. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of ISS Program Committee
  • Shigeru Horii; Momoko Yamaki; Masakazu Haruta; Jun-ichi Shimoyama
    T. IEE Japan 132 6 397  Institute of Electrical Engineers of Japan ({IEE} Japan) 2012年 [査読有り]
  • Momoko Yamaki; Shigeru Horii; Masakazu Haruta; Jun-ichi Shimoyama
    JAPANESE JOURNAL OF APPLIED PHYSICS 51 1 010107  2012年01月 [査読有り]
     
    Tri-axial orientation under modulated rotation magnetic fields (MRFs) and the growth of single crystals in ambient pressure were demonstrated in various REBa2Cu4O8 (RE124; RE, rare earth elements) compounds. RE124 crystals have been successfully grown for RE = Y, Sm, Eu, Gd, Dy, Ho, and Er. Optimal growth temperature regions for RE124 largely depended on the type of RE and became narrower in the case of lighter RE ions. By applying an MRF of 10 T, powders of all the grown RE124 were tri-axially oriented in epoxy resin at room temperature, and their orientation axes were clearly dependent on the type of RE ions in RE124. Furthermore, it was found from the changes in the degree of orientation under three different MRF conditions that tri-axial single-ion magnetic anisotropies of heavy RE3+ ions were highest among magnetic anisotropies generated by Cu-O networks and RE3+ ions. The appropriate choice of RE ions in RE-based cuprate superconductors enables the reduction of the magnetic field required for the production of bulk and thick films based on the magnetic orientation technique. (C) 2012 The Japan Society of Applied Physics
  • M. Yamaki; S. Horii; M. Haruta; T. Maeda; J. Shimoyama
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 872 - 875 2011年11月 [査読有り]
     
    We report the rare-earth (RE)-dependent magnetization axes of REBa2Cu4O8, which was synthesized by a flux method under ambient pressure, using powder samples tri-axially oriented in a modulated rotating magnetic field of 10 T. By optimizing the growth temperature and cooling rate, RE124 crystals were successfully grown for RE = Y, Sm, Eu, Gd, Dy, Ho, and Er. From the X-ray diffraction measurement, the magnetically oriented directions were largely dependent on the type of RE ions of RE124. However, the tri-axial magnetic anisotropies of RE124 could be qualitatively understood in terms of the magnitude relation between the single-ion magnetic anisotropy of RE3+ ions and the magnetic anisotropy generated by the CuO2 plane and Cu-O chain. For the practical use of this magneto-scientific process, the control of magnetization axes and tri-axial magnetic anisotropies through crystallochemical control is indispensable. (C) 2011 Elsevier B.V. All rights reserved.
  • S. Horii; S. Okuhira; M. Yamaki; M. Haruta; T. Maeda; J. Shimoyama
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 867 - 871 2011年11月 [査読有り]
     
    We report the tri-axial grain-orientation effects under a modulated rotation magnetic field for (Y1-xErx)(2) Ba4Cu7Oy), [ (Y, Er)247]. The magnetic easy axis at room temperature was drastically changed around x similar to 0.1: however, the Er-doping levels for the conversion of magnetic easy axes from the c-axis to the ab-direction and from the a- to b-axes were quite different. Tr-axial single-ion magnetic anisotropy of Er3+ was roughly 10 times greater than tri-axial magnetic anisotropy generated by both the superconducting CuO2 plane and the blocking Cu-O chain layer. An appropriate choice of rare-earth (RE) ions in RE-based cuprate superconductors enables the reduction of the required magnetic field for the production of bulks and thick films based on the magnetic orientation technique. (C) 2011 Elsevier B.V. All rights reserved.
  • M. Haruta; T. Sueyoshi; T. Fujiyoshi; M. Mukaida; H. Kai; K. Matsumoto; P. Mele; T. Maeda; S. Horii
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 944 - 946 2011年11月 [査読有り]
     
    Irreversibility lines and distributions of local critical current density (J(cl)) based on the percolation transition model were affected by the growth temperature (T-s) in 3.5 wt.%-BaNb2O6-doped ErBa2Cu3Oy thin films. The vortex-Bose-glass-like state appeared by the introduction of nano-rods, and this vortex state was affected by T-s The shape and width of the J(cl) distribution strongly depended on T-s. These results are probably caused by variations of the density and the growth direction for nano-rods reflecting T-s. The growth temperature is an important factor to achieve higher critical current properties under magnetic fields for coated conductors of rare-earth-based cuprates with nano-rods. (C) 2011 Elsevier B.V. All rights reserved.
  • T. Maeda; S. Takechi; K. Yamasaki; S. Isono; T. Tashiro; M. Haruta; S. Horii
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 608 - 610 2011年11月 [査読有り]
     
    (Pb0.5Fe0.5)Sr-2(Y0.5Ca0.5)Cu2O2 is known to have so-called "1-2-1-2" crystallographic structure which is one of typical structures of high-temperature superconducting cuprates (HTSC's). While it possesses structural characteristics of HTSC's, superconductivity has not been reported so far. In this study, phase formation, electrical properties and structural characteristics of this compound are investigated. It is shown that this phase can be synthesized using several kinds of rare-earth element and that post-annealing in O-2 is effective for decreasing electrical resistivity. The latter suggests that this "1-2-1-2" can be made superconducting by appropriate carrier-doping into the [Cu-O-2] plane. Preliminary Rietveld structural refinement using powder X-ray diffraction data show that the initial structural model based on the nominal (Pb,Fe)Sr-2(Y,Ca)Cu2Oz is basically correct except for true site-distribution of Fe and Cu. (C) 2011 Elsevier B.V. All rights reserved.
  • 春田正和; 堀井滋
    高知工科大学紀要 8 1 81 - 87 高知工科大学 2011年07月 
    希土類系高温超伝導薄膜における実用レベルの磁場中臨界電流密度の実現を目的として、第二相であるナノロッドを超伝導母相中に導入し、成膜温度が臨界電流特性(不可逆曲線、電流-電圧特性)に与える影響を明らかにした。ナノロッドが一次元欠陥として作用すれば、磁場中臨界電流密度の向上が期待される。不可逆曲線からは欠陥導入による磁束状態の変化を評価でき、また電流-電圧特性から超伝導組織の均一性・高性能性を表す臨界電流密度の空間分布を評価できる。Ba-Nb-O系ナノロッドを導入したErBa2Cu3Oy薄膜において、一次元欠陥導入時に特徴的なBoseグラス的磁束状態に起因した不可逆曲線が現れ、成膜温度によって不可逆曲線の振る舞い及び、臨界電流密度の空間分布が変化することを見出した。これらの結果は、成膜温度によってナノロッドの密度および形態が変化することにより、磁場中超伝導特性が大きく変化したことを示唆する。本研究から、磁場中送電能力の高い希土類系高温超伝導線材の製造プロセスの制御因子としての成膜温度の重要性が明らかとなった。査読あり論文
  • S. Horii; H. Ogino; M. Yamaki; M. Haruta; T. Maeda; J. Shimoyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 3 2741 - 2744 2011年06月 [査読有り]
     
    Tri-axial orientation of twin-free powder of Y2Ba4Cu7O15-delta (Y247) and uni-axial orientation of various FeAs-based compounds were attempted using modulated rotating and rotating magnetic fields, respectively. Tri-axial orientation with high degrees of inplane and c-axis orientation of Y247 was achieved under magnetic fields above 5 T, while magnetic fields at which reduction of the degrees began were different. We found from these crossover fields that quantitative magnetic anisotropy could be obtained. This determination method is particularly useful in that single crystalline samples are not required. From the magnetic orientation using the rotating field, all the obtained FeAs-based compounds showed a hard axis of magnetization parallel to the c-axis direction. On the other hand, the degrees of c-axis orientation were dependant on the types of ions in the blocking layers, and almost complete c-axis orientation was achieved for the compounds with transition-metal ions containing 3d electrons. Magnetic orientation using powder samples is a strong tool for the clarification of physical properties of Cooper pairs and critical current properties in FeAs-based superconductors.
  • Haruta M; Sakai S
    Superconductor Science and Technology 23 11 2010年11月 [査読有り]
     
    Thin films of Bi2Sr2CaCu2O8+delta (Bi-2212) covered by layers of Ag in selected regions were grown by pulsed-laser deposition with subsequent annealing. The grain size at the Ag-covered region was as large as 60-90 mu m. These grains were about three times as large as those in conventional films lacking the covering layer of silver, and the optimal annealing temperature for the silver-covered films was 15 degrees C lower than that for the uncovered films. The technique was adopted for use in the fabrication of intrinsic Josephson junctions (IJJs). The mesa structure for IJJs was fabricated on a Bi-2212 film with a 60 nm thick layer of silver annealed at 876 degrees C, and the resulting IJJs exhibited current-voltage characteristics that showed clear multiple branches.
  • 藤吉 孝則; 末吉 哲郎; 春田 正和; 米倉 健志; 池上 知顯; 石川 法人; 淡路 智; 渡辺 和雄
    低温工学 44 12 517 - 522 公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会) 2009年12月 [査読有り]
     
    The effects of columnar defects on the critical current density (Jc) and electric (E) vs. current density (J) characteristics were investigated for a YBa2Cu3Oy thin film prepared using a pulsed-laser deposition method. The YBa2Cu3Oy thin film was irradiated with 200 MeV Au ions from a direction θ=8.8°off the c-axis. Two peaks in the angular dependence of Jc were observed at the angles of θ=8.8°and θ=90°. These angles correspond to the directions of the columnar defect and intrinsic pinning, respectively. The E-J characteristics at various magnetic field angles can be described by the percolation transition model. The value of pinning parameter m increases at the angles of θ=8.8°and θ=90°. This result indicates that the efficiency of flux pinning is enhanced because fluxoids are effectively pinned by the columnar defects and intrinsic pinning or stacking faults in these directions.
  • Masakazu Haruta; Eiji Kume; Shigeki Sakai
    Supercond. Sci. Technol. 22 12 125004  {IOP} Publishing 2009年12月 [査読有り]
     
    Intrinsic Josephson junctions were fabricated on Bi2Sr2CaCu2O8+delta thin films. The thin films were prepared by a pulsed-laser-deposition technique at the substrate temperature of 500. C. The deposited films were annealed at 884-890 degrees C for crystallization. Bi2Sr2CaCu2O8+delta thin films were successfully obtained with the stoichiometric composition. At the annealing temperature of 888 degrees C, a film consisting of large crystalline grains has been obtained; a flat terrace area reaches several tens of mu m and is larger than the typical mesa size for the intrinsic Josephson junction. The mesa structure patterned on the annealed film has exhibited clear multiple branches in the current-voltage characteristic peculiar to the intrinsic Josephson junctions.
  • T. Fujiyoshi; M. Haruta; T. Sueyoshi; K. Yonekura; M. Watanabe; M. Mukaida; R. Teranishi; K. Matsumoto; Y. Yoshida; A. Ichinose; S. Horii; S. Awaji; K. Watanabe
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 468 15-20 1635 - 1637 2008年09月 [査読有り]
     
    Flux pinning properties in ErBa2Cu3Oy and YBa2Cu3Oy thin films with BaZrO3 nano-rods prepared by PLD were measured to investigate the flux pinning mechanism. The enhancement of J(c) was confirmed by the measurement of the dependence of J(c) on magnetic field. The angular dependence of J(c) has a broad peak at B parallel to c-axis. This result indicates that the BaZrO3 nano-rods work as the c-axis-correlated pinning centers, The pinning parameter m was evaluated from the electric fields versus current density characteristics and the peak of m appears in the magnetic field dependence. The characteristic behavior of m is caused by the matching of the density of BaZrO3 nano-rods with that of fluxoids. It is found that the relative distribution width of the local critical current density for the ErBa2Cu3Oy film with BaZrO3 nano-rods is smaller than that of the YBa2Cu3Oy films with BaZrO3 nano-rods. (C) 2008 Elsevier B.V. All rights reserved.
  • Sueyoshi T; Watanabe M; Haruta M; Fujiyoshi T; Miyahara K; Ikegami T; Ebihara K; Miyagawa R
    Physica C: Superconductivity and its Applications 468 15-20 1266 - 1269 2008年09月 [査読有り]
     
    We present the experimental studies on structures and superconducting properties of two different types of YBa2Cu3O7-delta multilayered films with second phases prepared by pulsed laser deposition. As second phase materials, Y2O3 and ZnO were inserted into films, respectively. The nano-particles were observed on a YBa2Cu3O7-delta layer when several pulses for second phase materials target ablation were chosen for both Y2O3 and ZnO. The critical temperatures of almost multilayered films were slightly reduced as compared to that of the pure YBa2Cu3O7-delta film, while the superconductivity was destroyed in the case of excess doping of ZnO. For half-multilayered films which consist of a lower layer with multilayer and an upper one with mono-YBa2Cu3O7-delta the most improved critical current densities were observed in both cases of Y2O3 and ZnO inclusions. This result indicates that there is a hope of further enhancement of critical current density by choosing the optimum in variety of spatial distributions of nano-particles, in addition to optimizing the dope level. (C) 2008 Elsevier B.V. All rights reserved.
  • M. Haruta; T. Fujiyoshi; R. Kajita; K. Yonekura; T. Sueyoshi; T. Doi; H. Kitaguchi; S. Awaji; K. Watanabe
    JOURNAL OF APPLIED PHYSICS 102 7 2007年10月 [査読有り]
     
    As-grown MgB2 thin films on Si substrates with high J(c) under magnetic fields were prepared by electron-beam evaporation. The value of J(c) has been enhanced by the deposition of MgB2 thin film in an O-2 atmosphere. The MgB2 thin film deposited in the O-2 atmosphere (O-2-doped film) has exhibited considerably higher J(c) in magnetic fields among MgB2 thin films reported before. It has been found that the high J(c) of the O-2-doped film is attributable to the flux pinning with grain boundaries strengthened by an introduction of MgO along grain boundaries. In a high magnetic field, a peculiar behavior of E-J characteristics where E-J curves vary in two stages was observed. This behavior also originates from the flux pinning with strengthened grain boundaries.
  • M. Hurata; T. Fujiyoshi; S. Kihara; T. Sueyoshi; K. Miyahara; Y. Harada; M. Yoshizawa; T. Takahashi; H. Iriuda; T. Oba; S. Awaji; K. Watanabe; R. Miyagawa
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 20 1 L1 - L4 2007年01月 [査読有り]
     
    As-grown MgB2 thin films were prepared by a MBE method under the conditions of low temperature, low deposition rate and high vacuum for applications in electric devices. The MgB2 thin films deposited on MgO and Ti buffered ZnO substrates have considerably higher J(c) under magnetic fields among MgB2 thin films reported before. The value of Jc for the MgB2 thin film deposited on Ti buffered ZnO has been 5.8 x 10(5) A cm(-2) at 10 K, 5 T in the magnetic field applied parallel to the c axis. In the angular dependence of J(c), the peak of J(c) attributable to c-axis-correlated pinning centres has been observed when the magnetic field was applied parallel to the c axis.
  • M. Haruta; T. Fujiyoshi; T. Sueyoshi; K. Dezaki; D. Ichigosaki; K. Miyahara; R. Miyagawa; M. Mukaida; K. Matsumoto; Y. Yoshida; A. Ichinose; S. Horii
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 19 8 803 - 807 2006年08月 [査読有り]
     
    ErBa2Cu3Oy (ErBCO) thin films with BaZrO3 (BZO) nanorods were prepared by a PLD method for an enhancement of the critical current density J(c). The values of J(c) for the ErBCO thin film containing 1.5 wt% BZO (Er15) in magnetic fields are higher than those for the ErBCO thin film containing 0.5 wt% BZO (Er05). The peaks of J(c) have been observed in the angular dependence of Jc in both the films when the magnetic field is applied parallel to the c-axis. It has been found that the peak is attributed to the flux pinning by BZO nanorods oriented parallel to the c-axis. The vortex glass - liquid transition temperature T-g and the pinning parameter m were derived by fitting observed electric transport properties to the theoretical expression based on the percolation transition model. The value of Tg of Er15 is higher than that of Er05. This result indicates that the vortex glass phase extends to a higher temperature region on increasing the fraction of BZO. The peak of m has been found in the magnetic field dependence. This fact is probably due to matching the density of BZO nanorods with that of fluxoids, which was confirmed by TEM observations.
  • M Haruta; T Fujiyoshi; T Sueyoshi; K Miyahara; T Doi; H Kitaguchi; S Awaji; K Watanabe
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 18 11 1460 - 1463 2005年11月 [査読有り]
     
    Critical current densities J(c) of MgB2 thin films have been measured; these were prepared by an electron beam evaporation method without any post-annealing. In order to improve the characteristics of J(c) in high magnetic fields, a MgB2 thin film was deposited in an O-2 atmosphere. The values of J(c) of the O-2-doped film have exceeded those of the non-doped film in magnetic fields applied perpendicular and also parallel to the c-axis. The peak of J(c) caused by the c-axis correlated pinning centres has been observed in the angular dependence of J(c). The upper critical field B-c2 and the vortex glass-liquid transition field B-g have been estimated from temperature dependences of resistivity curves in both directions of the magnetic fields perpendicular and parallel to the c-axis. It is found that B-c2 and B-g are increased by the introduction of O-2 in both the directions of the applied field. This fact indicates that effective pinning centres have been introduced by the deposition of the MgB2 thin film in an O-2 atmosphere.
  • M Haruta; T Fujiyoshi; T Sueyoshi; K Miyahara; T Doi; H Kitaguchi
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 426 I 174 - 178 2005年10月 [査読有り]
     
    The E-J characteristics of MgB2 thin film prepared by the electron beam evaporation method were investigated. The film has a fairly higher T-c of 35 K and J(c) of 0.48 MA/cm(2) at 20 K and 1 T among as-grown MgB2 films prepared by various methods. The E-J characteristics at various temperatures and magnetic fields can be described by the percolation transition model. The pinning parameters and the distribution of pinning forces of the MgB2 thin film were estimated. It was found that the MgB2 thin film has the uniform distribution of pinning forces by grain boundaries. (c) 2005 Elsevier B.V. All rights reserved.
  • T Fujiyoshi; M Haruta; K Yamafuji
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 424 1-2 29 - 39 2005年08月 [査読有り]
     
    As one of the bases of the theoretical estimation of the electromagnetic properties for practical purposes in wires, conductors and coils using high-T-c cuprate superconductors, the expression for the time decay of the magnetization in a slab sample of the high-T-c cuprate superconductor is derived by solving the Maxwell equations with the aid of the expression for the electric field, E, vs. current density, J, characteristic that was derived recently by the authors. The obtained expression, which is noticeably different from the one for the low-T-c metallic superconductors, is compared quantitatively with the numerical calculations, and the agreement between them seems to be satisfactory. (c) 2005 Elsevier B.V. All rights reserved.
  • Masakazu HARUTA; Takanori FUJIYOSHI; Tetsuro SUEYOSHI; Kuniyuki MIYAHARA; Toshiya DOI; Hitoshi KITAGUCHI; Satoshi AWAJI; Kazuo WATANABE
    Cryogenic Egineering 40 11 473 - 478 Cryogenic Association of Japan 2005年 [査読有り]
  • M Haruta; T Fujiyoshi; T Sueyoshi; K Miyahara; T Ikegami; K Ebihara; R Miyagawa; N Ishikawa; S Awaji; K Watanabe
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 412 SPEC. ISS. 511 - 514 2004年10月 [査読有り]
     
    The influence of columnar defects introduced by the heavy-ion irradiation on the pinning parameters in YBa2Cu3O7-delta thin films was investigated. The pinning parameters n, J(cm) and DeltaJ(c) were derived by fitting the experimentally obtained E-J characteristics to the theoretical curves calculated from the percolation transition model. The values of n and J(cm) have been increased and the value of DeltaJ(c), has been decreased by the introduction of columnar defects. (C) 2004 Elsevier B.V. All rights reserved.

MISC

書籍等出版物

  • EV用電池の安全性向上、高容量化と劣化抑制技術:表面被膜制御による鱗片状シリコン負極のサイクル寿命特性向上
    春田正和; 土井貴之; 稲葉稔 (担当:分担執筆範囲:pp. 256-261)技術情報協会 2023年11月
  • “Silicon LeafPowder® anode”, in: Kiyoshi Kanamura (Eds.), Next Generation Batteries –Realization of High Energy Density Rechargeable Batteries
    Masakazu Haruta, Takayuki Doi, Minoru Inaba (担当:分担執筆範囲:pp. 323-332)Springer 2021年03月
  • 春田正和; 稲葉稔; (監)境哲男 (担当:分担執筆範囲:3-10)シーエムシー出版 2019年11月 ISBN: 9784781314853 vii, 251p
  • 春田正和、土井貴之、稲葉稔;(編)技術情報協会 (担当:分担執筆範囲:155-161)技術情報協会 2019年11月 ISBN: 9784861047701 522p
  • 鱗片状シリコン負極のサイクル特性と劣化要因
    春田正和; 土井貴之; 稲葉稔; 富田明; 竹中利夫 (担当:共著範囲:pp.34-38)MATERIAL STAGE, Vol.17 (招待、解説記事) 2017年05月
  • 次世代リチウムイオン電池の実現に向けた取り組み
    稲葉稔; 春田正和; 橋之口道宏; 土井貴之 (担当:共著範囲:pp.314-318)ケミカルエンジニヤリング, Vol.61 (招待、解説記事) 2016年05月
  • 極めて低い電解質/電極界面抵抗を有する全固体リチウム電池の作製―液体電解質系リチウムイオン電池を凌駕する高速充放電に向けて―
    春田正和; 白木将; 一杉太郎 (担当:共著範囲:pp.116-117)自動車技術, Vol.69 (招待、解説記事) 2015年09月
  • 全固体リチウム電池の酸化物電解質/電極界面におけるイオン伝導特性
    春田正和; 白木将; 一杉太郎 (担当:共著範囲:pp.42-45)エネルギーデバイス Vol.2 (招待、解説記事) 2015年06月
  • 応用物理学的アプローチを活用した全固体Li電池研究:電極/電解質界面抵抗の低減に向けた界面研究
    白木将; 河底秀幸; 一杉太郎; 春田正和 (担当:共著範囲:pp.212-217)応用物理学会 有機分子・バイオエレクトロニクス分科会誌, Vol.26 (招待、解説記事) 2015年04月
  • イオン伝導経路を規定した電解質・電極界面尾イオン伝導性定量評価
    白木将; 春田正和; 一杉太郎 (担当:分担執筆範囲:pp.280-284)LiBの高容量・高耐久化のための電極―電解液(質)の界面制御技術と解析・評価方法 (技術情報協会出版) (依頼執筆) 2015年02月
  • 磁気科学プロセスのための層状機能性物質の磁気異方性制御
    堀井滋; 山木桃子; 奥平翔太; 春田正和 (担当:共著範囲:pp.194-201)化学工業, Vol.64 (招待、解説記事) 2013年03月
  • 酸素中成膜によりピンニングセンターを導入したSi基板MgB2薄膜の磁束ピンニング特性
    春田正和; 藤吉孝則; 梶田龍; 米倉健志; 末吉哲郎; 土井俊哉; 北口仁; 淡路智; 渡辺和雄 (担当:共著範囲:pp.4-6)未踏科学技術協会超伝導科学技術研究会 FSST NEWS, Vol.113 (招待、解説記事) 2007年

講演・口頭発表等

所属学協会

  • 低温工学・超電導学会   電気化学会   電気学会   応用物理学会   

共同研究・競争的資金等の研究課題

  • 全固体電池安定動作の要“電解質/電極界面イオン伝導”を操る
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2022年04月 -2025年03月 
    代表者 : 春田正和
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 春田 正和
     
    次世代のリチウムイオン電池用負極として大容量シリコン系材料の実用化を目指した。シリコン系負極の実用化においては、電池の劣化要因である電解液分解を抑制することが重要である。本研究では、フッ化リチウム(LiF)が電解液分解を抑制する重要な被膜成分であることを示した。フッ素系ポリマーであるNafionを添加したシリコン合材電極を作製することにより、初回充電時に電極表面にLiFを多く含んだ表面被膜が形成され、それ以降の充放電サイクルにおいて電解液分解を抑制すること明らかにした。さらに、シリコン系負極は全固体電池に適用させることも可能であり、優れた寿命特性を有することを示した。
  • 高エネルギー密度シリコン負極の実用化に向けた電極界面制御とイオン伝導機構の解明
    日本学術振興会:科学研究費補助金・基盤研究(B)
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 春田正和
  • 長尺高温超伝導線材の高性能化と安定製造に向けた材料設計
    日本学術振興会:科学研究費補助金・若手研究(B)
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 春田正和
  • ナノ欠陥を導入した希土類系高温超伝導薄膜のキャリア密度制御による高性能化
    日本学術振興会:科学研究費補助金・若手研究(B)
    研究期間 : 2011年04月 -2013年03月 
    代表者 : 春田正和
  • 超伝導/欠陥界面構造制御による実用的高温超伝導線材の製造技術の確立
    公益財団法人池谷科学技術振興財団:単年度研究助成‐A
    研究期間 : 2012年 -2012年 
    代表者 : 春田正和
  • 高温超伝導線材の実用化に向けた結晶組織制御と欠陥/超伝導界面構造の解明
    公益財団法人東電記念財団:平成23年度研究助成(電気・エネルギー一般研究)
    研究期間 : 2012年 -2012年 
    代表者 : 春田正和
  • JSAP-MRSジョイントシンポジウム若手研究者・技術者派遣助成
    応用物理学会:
    研究期間 : 2012年 -2012年 
    代表者 : 春田正和
  • ナノ欠陥の制御導入による実用的希土類系高温超伝導線材の製造技術の確立
    公益財団法人中部電気利用基礎研究振興財団:研究助成
    研究期間 : 2011年 -2011年 
    代表者 : 春田正和

その他

  • 2022年04月 - 2023年03月  近畿大学学内研究助成金、一般研究助成、No.IP005、脱炭素のキーデバイス“全固体電池”の実用化に向けた材料開発

その他のリンク