Performance information

• Melt growth of crystalline α-SrSi2 by the vertical Bridgman method and its thermoelectric characteristics　　　　　　　　　　　　　　　
  Haruno Kunioka; Shiori Iida; Kosuke Kimura; Yuto Shioya; Yuki Hiraoka; Yoji Imai; Naomi Hirayama; Tsutomu Iida
  Journal of Crystal Growth, Volume：645, First page：127838, Last page：127838, Nov. 2024, [Reviewed]
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2024.127838
  DOI ID：10.1016/j.jcrysgro.2024.127838, ISSN：0022-0248
• Study on the possibility of band gap widening of thermoelectric semiconductor α-SrSi2 by isoelectronic elements incorporation　　　　　　　　　　　　　　　
  Yuki Hiraoka; Yoji Imai; Tsutomu Iida; Haruno Kunioka
  Computational Condensed Matter, Volume：40, First page：e00932, Last page：e00932, Sep. 2024, [Reviewed]
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.cocom.2024.e00932
  DOI ID：10.1016/j.cocom.2024.e00932, ISSN：2352-2143
• Investigation of group 13 elements as potential candidates for p-type dopants in the narrow-gap thermoelectric semiconductor α-SrSi2
  Haruno Kunioka; Daishi Shiojiri; Shinta Takahashi; Kota Hiratsuka; Masato Yamaguchi; Naomi Hirayama; Yoji Imai; Motoharu Imai; Tsutomu Iida
  Journal of Materials Science, Volume：59, Number：18, First page：7840, Last page：7853, Apr. 2024, [Reviewed]
  Abstract
  
  To investigate the possibility of p-type doping of α-SrSi₂, a promising as an eco-friendly thermoelectric material, the energy changes of substitutions of the Si site of α-SrSi₂ by group 13 elements were evaluated using first-principles calculations. It is found that Ga doping was the most energetically favorable dopant while In is the most unfavorable. We examined the synthesis of Ga- and In-doped α-SrSi₂ using the vertical Bridgeman method and investigated their thermoelectric properties. The Ga atoms were doped to α-SrSi₂ successfully up to 1.0 at. %, while In atoms could not be doped as suggested by calculations. For experimental prepared Ga-doped samples, the carrier density was observed to increase with Ga doping, from 3.58 × 10¹⁹ cm⁻³ for undoped α-SrSi₂ to 4.49 × 10²⁰ cm⁻³ for a 1.0 at. % Ga-doped sample at 300 K. The temperature dependence of carrier concentrations was observed to change from negative to positive with increasing Ga content. In addition, the temperature dependence of the Seebeck coefficient was also observed to change from negative to positive with increasing Ga content. The results indicate that α-SrSi₂ undergoes a semiconductor–metal transition with Ga doping. The power factor for the undoped sample was quite high, at 2.5 mW/mK², while the sample with 0.3 at. % Ga had a value of 1.1 mW/mK² at room temperature.
  Springer Science and Business Media LLC, Scientific journal
  DOI：https://doi.org/10.1007/s10853-024-09653-x
  DOI ID：10.1007/s10853-024-09653-x, ISSN：0022-2461, eISSN：1573-4803
• Thermoelectric properties of yttrium-doped Mg3(Sb,Bi)2 synthesized by melting method　　　　　　　　　　　　　　　
  K. Kihou; H. Kunioka; H. Nishiate; C.H. Lee
  Journal of Materials Research and Technology, Volume：10, First page：438, Last page：444, Jan. 2021, [Reviewed]
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.jmrt.2020.12.008
  DOI ID：10.1016/j.jmrt.2020.12.008, ISSN：2238-7854
• Thermoelectric properties of NaZn4CuAs3 crystalized in the rhombohedral structure　　　　　　　　　　　　　　　
  Aichi Yamashita; Kunihiro Kihou; Haruno Kunioka; Hirotaka Nishiate; Atsushi Yamamoto; Yosuke Goto; Yoshikazu Mizuguchi; Tsutomu Iida; Yoshihiko Takano; Chul-Ho Lee
  Journal of Solid State Chemistry, Volume：291, First page：121588, Last page：121588, Nov. 2020, [Reviewed]
  Elsevier BV, Scientific journal
  DOI：https://doi.org/10.1016/j.jssc.2020.121588
  DOI ID：10.1016/j.jssc.2020.121588, ISSN：0022-4596
• Thermoelectric Properties of La1-xSrxZnAsO
  Y. Kimura; H. Kunioka; K. Kihou; H. Nishiate; H. Usui; Y. Tokunaga; T. Iida; K. Kuroki; C. H. Lee
  Journal of Electronic Materials, Volume：49, Number：11, First page：6715, Last page：6720, Sep. 2020, [Reviewed]
  Springer Science and Business Media LLC, Scientific journal
  DOI：https://doi.org/10.1007/s11664-020-08439-6
  DOI ID：10.1007/s11664-020-08439-6, ISSN：0361-5235, eISSN：1543-186X
• Thermoelectric Properties of (Ba,K)Zn₂As₂ Crystallized in the ThCr₂Si₂-type Structure
  Haruno Kunioka; Kunihiro Kihou; Daichi Kato; Hidetomo Usui; Tsutomu Iida; Hirotaka Nishiate; Kazuhiko Kuroki; Atsushi Yamamoto; Chul-Ho Lee
  Inorganic Chemistry, Volume：59, Number：9, First page：5828, Last page：5834, Apr. 2020, [Reviewed]
  American Chemical Society (ACS), Scientific journal
  DOI：https://doi.org/10.1021/acs.inorgchem.9b02680
  DOI ID：10.1021/acs.inorgchem.9b02680, ISSN：0020-1669, eISSN：1520-510X
• Observation of Interface between Thermoelectric Material Zn4Sb3 and Electrodes by Resistance Scanning and Seebeck Coefficient Mapping Techniques
  H. Kunioka; H. Obara; A. Yamamoto; T. Iida
  MATERIALS TRANSACTIONS, Volume：59, Number：7, First page：1035, Last page：1040, Jul. 2018, [Reviewed]
  Japan Institute of Metals, Scientific journal
  DOI：https://doi.org/10.2320/matertrans.e-m2018814
  DOI ID：10.2320/matertrans.e-m2018814, ISSN：1345-9678, eISSN：1347-5320
• Effect of rattling motion without cage structure on lattice thermal conductivity in LaOBiS2−xSex
  C. H. Lee; A. Nishida; T. Hasegawa; H. Nishiate; H. Kunioka; S. Ohira-Kawamura; M. Nakamura; K. Nakajima; Y. Mizuguchi
  Applied Physics Letters, Volume：112, Number：2, Jan. 2018, [Reviewed]
  Low energy phonons in LaOBiS2−xSex are studied using inelastic neutron scattering. Dispersionless flat phonon branches that are mainly associated with a large vibration of Bi atoms are observed at a relatively low energy of E = 6–6.7 meV. The phonon energy softens upon Se doping presumably owing to its heavier atomic mass than the S atom and the expansion of the lattice constant. Simultaneously, the lattice thermal conductivity lowered upon Se doping as the same manner of the phonon softening. These suggest that despite the lack of an oversized cage in LaOBiS2−xSex, rattling motions of Bi atoms can scatter phonon like rattling in cage compounds, contributing to enhance the thermoelectric property.
  AIP Publishing, Scientific journal
  DOI：https://doi.org/10.1063/1.5010373
  DOI ID：10.1063/1.5010373, ISSN：0003-6951, eISSN：1077-3118
• Thermoelectric properties of (Ba,K)Cd₂As₂ crystallized in the CaAl₂Si₂-type structure
  H. Kunioka; K. Kihou; H. Nishiate; A. Yamamoto; H. Usui; K. Kuroki; C. H. Lee
  Dalton Transactions, Volume：47, Number：45, First page：16205, Last page：16210, 2018, [Reviewed]
  

  As-Based Zintl compounds Ba_1−xK_xCd₂As₂ crystallized in the CaAl₂Si₂-type structure (space group P3̄m1) were prepared using solid-state reactions followed by hot-pressing.

  
  Royal Society of Chemistry (RSC), Scientific journal
  DOI：https://doi.org/10.1039/c8dt02955e
  DOI ID：10.1039/c8dt02955e, ISSN：1477-9226, eISSN：1477-9234
• Electrical current dependence of the ionic conduction in Zn₄Sb₃
  Haruno Kunioka; Atsushi Yamamoto; Tsutomu Iida; Haruhiko Obara
  Applied Physics Express, Volume：10, Number：9, First page：095801, Last page：095801, Aug. 2017, [Reviewed]
  IOP Publishing, Scientific journal
  DOI：https://doi.org/10.7567/apex.10.095801
  DOI ID：10.7567/apex.10.095801, ISSN：1882-0778, eISSN：1882-0786

• Development of thermoelectric batteries composed of common elements and operating in the low temperature range (100-300 degreeC)　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), 01 Apr. 2023 - 31 Mar. 2026
  Tokyo University of Science
  Grant amount(Total)：46670000, Direct funding：35900000, Indirect funding：10770000
  Grant number：23H00189
• Development of environmentally friendly thermoelectric batteries adapt to recyclable society fabricated by Industrially suitable method　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists, 01 Apr. 2023 - 31 Mar. 2025
  Tokyo University of Science
  Grant amount(Total)：4680000, Direct funding：3600000, Indirect funding：1080000
  Grant number：23K13317