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小玉 翔平（コダマ ショウヘイ）
| 理工学研究科 物質科学部門 | 助教 |
| 工学部 応用化学科 |
業績情報
■ 論文- Modification of photoluminescence wavelength and decay constant of Cr:Gd3Ga5O12 substituted by Ca/Si cation pair
Natsuki Shimoyama; Shohei Kodama; Karol Bartosiewicz; Chihaya Fujiwara; Ikuo Yanase; Hiroaki Takeda
Journal of the Ceramic Society of Japan, 巻：132, 号：7, 開始ページ：364, 終了ページ：368, 2025年07月, ［査読有り］, ［責任著者］
Ceramic Society of Japan, 研究論文（学術雑誌）
DOI：https://doi.org/10.2109/jcersj2.23216
DOI ID：10.2109/jcersj2.23216, ISSN：1882-0743, eISSN：1348-6535 - Photoluminescence properties of solid solutions of YNbO4, GdNbO4 and LuNbO4
Hayato Sato; Shohei Kodama; Ikuo Yanase; Hiroaki Takeda
Journal of the Ceramic Society of Japan, 2025年, ［査読有り］, ［責任著者］
Ceramic Society of Japan, 研究論文（学術雑誌）
DOI：https://doi.org/10.2109/jcersj2.25015
DOI ID：10.2109/jcersj2.25015, ISSN：1882-0743, eISSN：1348-6535 - Flux growth and evaluation of optical properties of Ce doped Li
2 CaSiO4 as a candidate for noble neutron scintillator
Shohei Kodama; Taiga Nishii; Miki Sodeno; Yusuke Urano; Shunsuke Kurosawa; Ikuo Yanase; Hiroaki Takeda
Journal of the Ceramic Society of Japan, 巻：132, 号：7, 開始ページ：369, 終了ページ：374, 2024年07月, ［査読有り］, ［筆頭著者, 責任著者］
This study focuses on the growth of transparent single crystals of Li2CaSiO4 (LCS) doped with Ce as neutron scintillator candidates. LCS is a light material with a high melting point and chemical stability; thus, LCS is applicable for use in high-flux neutron environments. However, the growth of transparent single crystals from the melt has been difficult owing to the phase transitions. In this study, the LiF/LiCl eutectic was used as a flux with a lower melting point and less decomposition than LiCl, and Ce was selected as the luminescent center. The phase diagram of the LiF/LiCl-LCS system was determined, and the conditions for crystal growth were optimized, consequently, transparent non-doped LCS and Ce:LCS crystals were successfully obtained. The alpha-ray-excited scintillation spectrum and scintillation decay time of Ce:LCS were measured in a feasibility study for neutron detection. The results showed that Ce:LCS has potential as a neutron scintillator, with a significantly fast decay time of 28.46 ns.
研究論文（学術雑誌）
DOI：https://doi.org/10.2109/jcersj2.23214
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DOI ID：10.2109/jcersj2.23214, ISSN：1882-0743, eISSN：1348-6535, SCOPUS ID：85197210970 - Capture of CO
2 from ambient air by sodium manganate and CO2 recovery at low temperatures
Ikuo Yanase; Hiroaki Nagashima; Teppei Okada; Shohei Kodama; Hiroaki Takeda
Journal of Physics and Chemistry of Solids, 巻：187, 2024年04月, ［査読有り］
Sodium manganate (Na0.66MnO2, NMO) was synthesized by a liquid method using NaOH, Mn(NO3)2, and ethylenediaminetetraacetate. The absorption of CO2 from air by NMO was investigated at room temperature. The CO2 absorption by NMO was promoted at high relative humidity (RH) and accompanied by the formation of birnessite and sodium carbonate hydrate phases. NMO efficiently absorbed CO2 from air when the RH was greater than 60 % because adsorption of water vapor to NMO readily occurred above 60 % RH. Thus, NMO absorbed CO2 together with H2O adsorbed from the air. The regeneration of NMO, was accompanied by the release of CO2 from sodium carbonate hydrates and occurred at temperatures as low as 150 °C. This behavior was attributed the similar structural features of NMO and birnessite, which both incorporate layered structures composed of MnO6 octahedra.
研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.jpcs.2024.111866
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DOI ID：10.1016/j.jpcs.2024.111866, ISSN：0022-3697, SCOPUS ID：85182418063 - Effect of strontium substitution on growth and piezoelectric properties of calcium magnesium silicate Ca
2 MgSi2 O7 single crystals
Hiroaki Takeda; Takumi Uehara; Genki Hirano; Shohei Kodama; Ikuo Yanase; Kazumasa Sugiyama
Japanese Journal of Applied Physics, 巻：62, 号：SM, 2023年11月, ［査読有り］
We report the effect of Sr substitution on the crystal growth and piezoelectric properties of calcium magnesium silicate Ca2MgSi2O7 (CMS) single crystals. Strontium-substituted CMS single crystals with a chemical composition of Ca1-x Srx MgSi2O7 (CSMS100x; x = 0.0 to 0.6) were grown using the conventional Czochralski method. CSMS100x crystals without impurity phases are obtained up to x = 0.5. Both crystallographic axis c and a increased with the Sr content x, and the crystallographic axis ratio a/c decreased. The piezoelectric d 36 constants obtained using CMS, CSMS30, and CSMS40 crystals decreased with an increase in the Sr content x. Based on these observations, a relationship between piezoelectric properties and crystal structure was found using data from 14 types of melilite-type crystals. It was found that d 36 increases with an increase in a/c.
研究論文（学術雑誌）
DOI：https://doi.org/10.35848/1347-4065/acf2a5
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DOI ID：10.35848/1347-4065/acf2a5, ISSN：0021-4922, eISSN：1347-4065, SCOPUS ID：85173570806 - Spark plasma sintering and ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 fine particles synthesized by glass crystallization
Tatsuya Tezuka; Yuma Inagaki; Shohei Kodama; Hiroaki Takeda; Ikuo Yanase
Powder Technology, 巻：429, 開始ページ：118870, 終了ページ：118870, 2023年11月, ［査読有り］
Elsevier BV, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.powtec.2023.118870
DOI ID：10.1016/j.powtec.2023.118870, ISSN：0032-5910 - Structure Analysis and Luminescence Properties of Red-emitting Iodide Scintillators with Potassium-hexachloroplatinate(IV) Type Structure
Shohei Kodama; Shunsuke Kurosawa; Kotaro Fujii; Masatomo Yashima; Akihiro Yamaji; Akira Yoshikawa
Journal of Alloys and Compounds, 開始ページ：172506, 終了ページ：172506, 2023年10月, ［査読有り］, ［筆頭著者］
Elsevier BV, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.jallcom.2023.172506
DOI ID：10.1016/j.jallcom.2023.172506, ISSN：0925-8388 - Optical and scintillation properties of Yb-doped La2Hf2O7 crystal grown by core heating method for fiber reading remote-dosimetry system
Satoshi Ishizawa; Shunsuke Kurosawa; Yutaro Kurashima; Shohei Kodama; Yuki Morishita; Akihiro Yamaji; Maki Ohno; Shiori Ishikawa; Masateru Hayashi; Makoto Sasano; Taisuke Makita; Chihaya Fujiwara; Vladimir Kochurikhin; Akira Yoshikawa; Takushi Takata; Hiroki Tanaka
OPTICAL MATERIALS, 巻：142, 2023年08月, ［査読有り］
(La0.99Yb0.01)2Hf2O7 (Yb:LaHO) crystal has been developed by the core heating method as a near-infraredemitting oxide scintillator for a fiber reading remote-dosimetry system under the high-dose-rate region. This system consists of a scintillator, a long silica optical fiber and a detector unit. Near-infrared-emitting photons can be separated from significant fiber-derived noise mainly observed in the UV-blue range. The noise is generated in the optical fiber itself by gamma-rays and charged particles. The Yb:LaHO crystal had a maximum emission peak at 975 nm when excited by X-rays and a transmittance of approximately 29% at 977 nm. The afterglow intensity of the Yb:LaHO crystal under X-rays was 11% that of Cr:& alpha;-Al2O3 (ruby) crystal. We demonstrated the applicability of the remote-dosimetry system with the Yb:LaHO crystal irradiated with gamma rays from a 60Co source with an activity of -77 TBq. The signal-to-noise ratio (SNR) of the Yb:LaHO crystal was 1.9 times higher than that of the ruby crystal at - 1 kGy/h, and the lowest limit of the dynamic range was comparable between the Yb: LaHO and ruby crystals. The results of the SNR and afterglow intensity showed that the Yb:LaHO crystal is a more suitable scintillator than the ruby crystal for fiber reading remote-dosimetry systems.
ELSEVIER, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.optmat.2023.113941
DOI ID：10.1016/j.optmat.2023.113941, ISSN：0925-3467, eISSN：1873-1252, Web of Science ID：WOS:001028151700001 - Synthesis and photoluminescence properties of divalent rare-earth-doped Li2CaSiO4
Shohei Kodama; Tomoki Saito; Ikuo Yanase; Hiroaki Takeda
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 巻：131, 号：7, 開始ページ：258, 終了ページ：262, 2023年07月, ［査読有り］, ［筆頭著者, 責任著者］
As potential candidates for neutron scintillators, divalent rare-earth-doped Li2CaSiO4 (Ln:LCS) phosphors were synthesized and their photoluminescence (PL) properties were evaluated. LCS is as light as LiCaAlF6 and has a low density of 2.86 g/cm3 and a small effective atomic number of 14. In this study, a ferrosilicon powder was used as a safe and convenient reductive medium for the reduction of Ln3+ to Ln2+. Sm, Eu, and, Yb were doped into LCS, where they occupied the Ca2+ sites. Among the phosphors synthesized by embedding in the ferrosilicon powder, Eu:LCS, Yb:LCS, and Eu,Yb:LCS exhibited luminescence arising from 5d-4f electronic transitions of the divalent emitter ion. All three divalent ion-doped phosphors had slower PL decay components with lifetimes of the order of tens of microseconds. Although Ln:LCS appears to be unsuitable for neutron detection under high doses owing to the slow decay of the doped Ln2+ emission, the phosphors, notably Eu2+ phosphors, have relatively high emission intensities and can potentially be applied as high-temperature neutron scintillators. & COPY;2023 The Ceramic Society of Japan. All rights reserved.
CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.2109/jcersj2.22163
DOI ID：10.2109/jcersj2.22163, ISSN：1882-0743, eISSN：1348-6535, Web of Science ID：WOS:001022446500001 - Synthesis and ionic conductivity of NASICON-type Li1.4Al0.4Ti1.6(PO4)(3) fine powder by a novel multi-step glass crystallization method
Tatsuya Tezuka; Kouki Kuribara; Shohei Kodama; Hiroaki Takeda; Ikuo Yanase
JOURNAL OF NON-CRYSTALLINE SOLIDS, 巻：590, 2022年08月, ［査読有り］
Li1.4Al0.4Ti1.6(PO4)(3) (LATP) with a Na super ionic conductor (NASICON)-structure was successfully synthesized by a novel glass-crystallization method. First, glass specimens were prepared by heating raw materials LiPO3, Li2CO3, Al(PO3)(3), and TiO2 at 1300 C for 1 h in air, and then a two-step heat treatment was performed on the glass specimens to synthesize the LATP. Li2Ti2(PO4)(3) particles formed in the glass specimen during the first heat treatment at 460C for 2 h, followed by a change of Li2Ti2(PO4)3 to LATP during the second heat treatment at 720C for 20 h. The resultant fine LATP powder had a sharp particle-size distribution with a 50% integrated diameter of 1.9 mu m. The ionic conductivity of the LATP-sintered body that was fabricated at 1000 C by using the LATP fine powder was 1.34 x 10(-5) S cm-1 at 25 C, which was superior to that obtained by a conventional method.
ELSEVIER, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.jnoncrysol.2022.121675
DOI ID：10.1016/j.jnoncrysol.2022.121675, ISSN：0022-3093, eISSN：1873-4812, Web of Science ID：WOS:000802616900004 - Growth and characterization of strontium-substituted La3Ta0.5Ga5.5O14 single crystals
Hiroaki Takeda; Yudai Sobata; Haruki Usui; Shohei Kodama; Ikuo Yanase; Takuya Hoshina; Takaaki Tsurumi; Kiyoshi Shimamura
Journal of the Ceramic Society of Japan, 巻：130, 号：1, 開始ページ：16, 終了ページ：20, 2022年01月, ［査読有り］
The effects of strontium substitution on the electrical properties of La3Ta0.5Ga5.5O14 (LTG) are reported. Strontium substituted LTG (Sr-LTG) with a nominal chemical composition La2.9Sr0.1Ta0.55Ga5.45O14 crystals were grown using the conventional Czochralski method under high and low oxygen partial pressures. The electrical properties and thermal behaviors of the Sr-LTG crystals were also compared with those of pure crystals. Sr substitution was found to affect the electroacoustic constants and thermal expansion coefficient clearly. These characteristics are discussed from crystallographic perspectives. The Sr-LTG crystals grown at low oxygen partial pressures exhibited higher electrical resistivity ? for pressure sensors used at high temperatures.
研究論文（学術雑誌）
DOI：https://doi.org/10.2109/jcersj2.21116
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DOI ID：10.2109/jcersj2.21116, ISSN：1882-0743, eISSN：1348-6535, SCOPUS ID：85122830537 - Na-ion conductivity of beta-NaFeO2 synthesized from an EDTA chelate complex
Ikuo Yanase; Naoki Kuwada; Kouki Kuribara; Shohei Kodama; Hiroaki Takeda
INORGANIC CHEMISTRY COMMUNICATIONS, 巻：134, 2021年12月, ［査読有り］
In this study, Na-ion conductivity of beta-NaFeO2 was improved by a low-temperature synthesis. A precursor Fecomplex containing ethylenediamine tetraacetate (EDTA) was prepared and then calcined at temperatures of 500-800 degrees C under flowing air (on heating) and Ar gas (on cooling). Single-phase beta-NaFeO2 powder was obtained at temperatures of 600-750 degrees C. The specific surface area of the beta-NaFeO2 powder increased as the calcination temperature decreased. The beta-NaFeO2 compact fabricated from the powder calcined at 600 degrees C had the largest density. Alternating current impedance analysis revealed that the resistivity of the grain boundaries in the compact decreased with increasing density, which improved the Na-ion conductivity of beta-NaFeO2. Thus, the Naion conductivity of beta-NaFeO2 was successfully improved by increasing its specific surface area.
ELSEVIER, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.inoche.2021.108913
DOI ID：10.1016/j.inoche.2021.108913, ISSN：1387-7003, eISSN：1879-0259, Web of Science ID：WOS:000710197900002 - Cs2HfCl6 doped with Zr: Influence of tetravalent substitution on scintillation properties
V. Vaněček; J. Páterek; R. Král; M. Buryi; V. Babin; K. Zloužeová; S. Kodama; S. Kurosawa; Y. Yokota; A. Yoshikawa; M. Nikl
Journal of Crystal Growth, 巻：573, 2021年11月, ［査読有り］
Homeland security is an emerging application field for inorganic scintillators. Detection and identification of radioactive materials in both individual and cargo transport requires scintillators with excellent energy resolution and high light output. On the other hand, the time characteristics of the scintillation are less crucial. Furthermore, price is a key parameter due to the large volume of the detectors. State-of-the-art halide scintillators e. g. SrI2:Eu or LaBr3:Ce can satisfy the requirements for light yield and energy resolution, but the production costs are very high due to complicated crystal growth and the high prices of rare earth metals. Cesium hafnium chloride (Cs2HfCl6) is a promising intrinsic scintillator with high light yield and excellent resolution. Moreover, its low hygroscopicity and cubic crystal structure could allow lower production costs compared to SrI2 or LaBr3. Intrinsic luminescence of Cs2HfCl6 is commonly attributed to self-trapped excitons. However, the luminescence of Cs2HfCl6 shows complex structure and temperature dependence. This might be explained by the presence of zirconium which is a common impurity in hafnium compounds. We present a study of the influence of zirconium doping on the scintillation properties of Cs2HfCl6. Single crystals of Cs2HfCl6 with zirconium doping from 0 to 1 mol% were grown by the vertical Bridgman method. Their phase purity, radioluminescence, scintillation decay, light yield, and afterglow were evaluated. Results show that zirconium doping can affect the scintillation properties of Cs2HfCl6 even at concentrations comparable to impurity levels of zirconium in hafnium compounds.
研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.jcrysgro.2021.126307
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DOI ID：10.1016/j.jcrysgro.2021.126307, ISSN：0022-0248, SCOPUS ID：85113923028 - Thermal analysis of cesium hafnium chloride using DSC–TG under vacuum, nitrogen atmosphere, and in enclosed system
R. Král; P. Zemenová; V. Vaněček; A. Bystřický; M. Kohoutková; V. Jarý; S. Kodama; S. Kurosawa; Y. Yokota; A. Yoshikawa; M. Nikl
Journal of Thermal Analysis and Calorimetry, 巻：141, 号：3, 開始ページ：1101, 終了ページ：1107, 2020年08月, ［査読有り］
This paper reports on the preparation of undoped cesium hafnium chloride (Cs HfCl ) and study of its thermal properties. The Cs HfCl is considered, due to its excellent scintillation properties, as a promising candidate for cost-effective radiation detectors with potential to replace traditional halide scintillators, e.g., NaI:Tl and CsI:Tl. The Cs HfCl material was successfully synthesized from a cesium chloride and a hafnium chloride mixed together in stoichiometric ratio. The presence of only one crystalline phase of the Cs HfCl in the material was confirmed by the X-ray diffraction analysis. The simultaneous non-isothermal differential scanning calorimetry and thermogravimetry (DSC–TG) of the synthesized material under nitrogen atmosphere, vacuum, and in enclosed system was performed. The Cs HfCl decomposition and melting of CsCl–Cs HfCl mixture under nitrogen and vacuum were observed. On the contrary, the DSC measurement of the cesium hafnium chloride in enclosed system showed only one endothermic peak related to the congruent melting point. Furthermore, the repeated DSC–TG measurements to investigate the materials’ stability in enclosed system were carried out as well. 2 6 2 6 2 6 2 6 2 6 2 6
研究論文（学術雑誌）
DOI：https://doi.org/10.1007/s10973-019-09087-7
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DOI ID：10.1007/s10973-019-09087-7, ISSN：1388-6150, eISSN：1588-2926, SCOPUS ID：85076089834 - Single-crystal growth, structure and luminescence properties of Cs2HfCl3Br3
Shohei Kodama; Shunsuke Kurosawa; Kotaro Fujii; Taito Murakami; Masatomo Yashima; Jan Pejchal; Robert Kral; Martin Nikl; Akihiro Yamaji; Masao Yoshino; Satoshi Toyoda; Hiroki Sato; Yuji Ohashi; Kei Kamada; Yuui Yokota; Akira Yoshikawa
OPTICAL MATERIALS, 巻：106, 2020年08月, ［査読有り］, ［筆頭著者］
Single crystal of the mixed-halogen compound Cs2HfCl3Br3 was grown by the vertical Bridgman method, and we investigated its crystal structure and optical properties. Single-crystal X-ray diffraction and energy dispersive Xray spectroscopy analyses indicated the chemical composition to be Cs2Hf(Cl0.578(6)Br0.422(6)) 6 (= Cs2HfCl3.47 (4)Br2.53(4), approximately Cs2Hf(Cl058Br0.42)(6)) where the number in the parentheses denotes the estimated standard deviation in the last digit. Cs2Hf(Cl0.58Br0.42)(6) was found to have a cubic Fm (3) over barm potassium hexachloroplatinate structure consisting of Cs+ cations and Hf(Cl0.58Br0.42)(6)(2-) anions. The emission peak of Cs2HfCl3Br3 was red-shifted by Br substitution, and the photoluminescence decays of Cs2HfCl3Br3 were accelerated when compared to those of Cs2HfCl6. Cs2HfCl3Br3 had an emission peak at 450 nm under X-ray irradiation, while under UV-excitation, two photoluminescence emission peaks at 420 and 525 nm were observed. The decay profile of the 420-nm emission band had a single-exponential component with a decay time of 1.95. 0.01 mu s under the 280-nm-excitation. On the other hand, 525-nm-emisison had two decay components of 0.28. 0.03 mu s (11%) and 6.54. 0.03 mu s (89%) under 305-nm-photons excitation.
ELSEVIER, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.optmat.2020.109942
DOI ID：10.1016/j.optmat.2020.109942, ISSN：0925-3467, eISSN：1873-1252, Web of Science ID：WOS:000542134200008 - Growth and Scintillation Properties of a New Red-Emitting Scintillator Rb2HfI6 for the Fiber-Reading Radiation Monitor
Shohei Kodama; Shunsuke Kurosawa; Yuki Morishita; Hiroshi Usami; Tatsuo Torii; Masateru Hayashi; Makoto Sasano; Tetsushi Azuma; Hiroki Tanaka; Vladimir Kochurikhin; Jan Pejchal; Robert Kral; Masao Yoshino; Akihiro Yamaji; Satoshi Toyoda; Hiroki Sato; Yuji Ohashi; Yuui Yokota; Kei Kamada; Martin Nikl; Akira Yoshikawa
IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 巻：67, 号：6, 開始ページ：1055, 終了ページ：1062, 2020年06月, ［査読有り］, ［筆頭著者］
A new red-emitting halide scintillator Rb2HfI6 was developed using the vertical Bridgman furnace and quartz ampoule. Under X-ray irradiation, Rb2HfI6 had a broad emission band of around 725 nm. The light output and energy resolution were determined to be similar to 40 000 photons/MeV and similar to 7.4% (fullwidth at half-maximum at 662 keV), respectively. Since red photons are transmitted with smaller losses than blue or yellow photons inside an optical fiber, a long-fiber- reading radiation detection system using the high light-output red scintillator can be established for severe or hazardous environments. We fabricated the Rb2HfI6 scintillation crystal and performed the gamma-ray detection test under high-dose irradiation condition from a Co-60 source with an activity of similar to 100 TBq. The dynamic range of the Rb2HfI6 gamma-ray detection with a 20-m optical fiber was evaluated and compared with the previously developed Cs2HfI6 crystal and the conventional deep-red Cr: alpha-Al2O3 (ruby) scintillator. The gamma-ray doses from similar to 0.4 to similar to 1 kSv/h were successfully measured using Rb2HfI6 through the 20-m fiber.
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1109/TNS.2020.2976695
DOI ID：10.1109/TNS.2020.2976695, ISSN：0018-9499, eISSN：1558-1578, Web of Science ID：WOS:000545005000035 - Fiber-read radiation monitoring system using an optical fiber and red-emitting scintillator for ultra-high-dose conditions
Shohei Kodama; Shunsuke Kurosawa; Maki Ohno; Yuki Morishita; Hiroshi Usami; Masateru Hayashi; Makoto Sasano; Tetsushi Azuma; Hiroki Tanaka; Vladimir Kochurikhin; Akihiro Yamaji; Masao Yoshino; Satoshi Toyoda; Hiroki Sato; Yuji Ohashi; Kei Kamada; Yuui Yokota; Akira Yoshikawa; Tatsuo Torii
APPLIED PHYSICS EXPRESS, 巻：13, 号：4, 2020年04月, ［査読有り］, ［筆頭著者］
We have developed a remote scintillation detector using a CCD spectrometer and a red-emitting scintillator coupled with a 20 m optical fiber for ultra-high-dose conditions. Gamma rays were detected with a conventional deep-red-emitting ruby scintillator and Cs2HfI6, which is a novel material with 700 nm red emission and a high light output. The scintillators were irradiated with gamma rays from a Co-60 source under an effective dose rate from similar to 0.002 to similar to 1 kSv h(-1). The integrated area of the Cs2HfI6 emission spectra was larger than that of the ruby, and good linearity of the Cs2HfI6 signal as a function of dose rate was confirmed.
IOP PUBLISHING LTD, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.35848/1882-0786/ab77f7
DOI ID：10.35848/1882-0786/ab77f7, ISSN：1882-0778, eISSN：1882-0786, Web of Science ID：WOS:000521379100001 - Modified vertical Bridgman method: Time and cost effective tool for preparation of Cs2HfCl6 single crystals
V. Vanecek; R. Kral; J. Paterek; V. Babin; V. Jary; J. Hybler; S. Kodama; S. Kurosawa; Y. Yokota; A. Yoshikawa; M. Nikl
Journal of Crystal Growth, 巻：533, 2020年03月, ［査読有り］
Time and cost effective methods are highly desirable in research and development of new scintillators. Modern techniques like micro-pulling down (μ-PD) are suitable for material screening but are unfit for the growth of some crystals. These crystals must be grown by different methods that are usually very time demanding. Modification of halide μ-PD apparatus by custom made elements allowed us to grow cesium hafnium chloride (Cs2HfCl6) by vertical Bridgman method (VB) with significantly reduced growth time. Structural and optical properties of samples prepared from as-grown crystals were studied and compared to crystals grown by standard VB method. The X-ray diffraction confirmed the formation of cesium hafnium chloride single-phase and natural cleavage of the crystals along the (1 1 1) crystallographic plane. Photoluminescence emission, excitation, absorption, and radioluminescence spectroscopy revealed that the optical quality of the crystals grown by modified VB method was comparable to the quality of the crystals grown by standard VB method. Therefore we can use samples prepared by modified VB to estimate and optimize the performance of Cs2HfCl6 based crystals in scintillation detectors. This setup allows the time and cost-effective material screening and it is a powerful tool for the development of new halide based single crystal scintillators.
研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.jcrysgro.2020.125479
Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85077646276&origin=inward
Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85077646276&origin=inward
DOI ID：10.1016/j.jcrysgro.2020.125479, ISSN：0022-0248, SCOPUS ID：85077646276 - Development of a novel red-emitting cesium hafnium iodide scintillator
Shohei Kodama; Shunsuke Kurosawa; Maki Ohno; Akihiro Yamaji; Masao Yoshino; Jan Pejchal; Robert Kral; Yuji Ohashi; Kei Kamada; Yuui Yokota; Martin Nikl; Akira Yoshikawa
RADIATION MEASUREMENTS, 巻：124, 開始ページ：54, 終了ページ：58, 2019年05月, ［査読有り］, ［筆頭著者］
Cesium hafnium iodide (CHI) was reported as a novel red-emitting scintillator in our previous article, while optimization of the crystal quality and evaluation of the scintillation performance were insufficient. In this study, a large and transparent CHI single crystalline specimen was obtained using slow crystal growth speed. Coupled with a Si avalanche photo-diode, the full width at half maximum energy resolution was evaluated to be 4.2 +/- 0.2% at 662 keV which was the best value among conventional red-emitting scintillators. The scintillation light output, non-proportional response of light output and scintillation decay were also evaluated with a photomultiplier tube.
PERGAMON-ELSEVIER SCIENCE LTD, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.radmeas.2019.03.005
DOI ID：10.1016/j.radmeas.2019.03.005, ISSN：1350-4487, Web of Science ID：WOS:000468708600009 - Growth and Luminescent Properties of Cs2HfCl6 Scintillators Doped With Alkaline Earth Metals
Shohei Kodama; Shunsuke Kurosawa; Jan Pejchal; Robert Kral; Akihiro Yamaji; Yuji Ohashi; Yuui Yokota; Kei Kamada; Martin Nikl; Akira Yoshikawa
IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 巻：65, 号：8, 開始ページ：2169, 終了ページ：2173, 2018年08月, ［査読有り］, ［筆頭著者］
Nondoped Cs2HfCl6 (CHC) and alkaline earth metal-doped CHC (AE:CHC) crystals were grown by the vertical Bridgman-Stockbarger method. The spectra of the AE:CHC under X-ray excitation were similar to those for the AE-free crystal; thus, AE doping did not change emission wavelength of CHC. We determined the light outputs and energy resolutions of nondoped CHC and AE:CHC by measuring pulse-height spectra under 662-keV gamma-ray excitation of a Cs-137 source. Both light output and energy resolution were deteriorated with AE doping. For example, nondoped CHC had a light output of similar to 44 000 photons/MeV and energy resolution of similar to 5.2%; on the other hand, Sr 0.5 at.%-doped CHC had a light output of only similar to 28 000 photons/MeV and energy resolution of similar to 10%. Scintillation decay also did not change. The nonproportional response values of light output versus gamma-ray energy did not improve in AE:CHC either. Therefore, doped AEs can be responsible for creation of defect trap levels which would hamper the carrier transport in CHC structure.
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1109/TNS.2018.2848474
DOI ID：10.1109/TNS.2018.2848474, ISSN：0018-9499, eISSN：1558-1578, Web of Science ID：WOS:000442365000032 - Comprehensive Study on Ce-Doped (Gd,La)(2)Si2O7 Scintillator
Shunsuke Kurosawa; Takahiko Horiai; Rikito Murakami; Yasuhiro Shoji; Jan Pejchal; Akihiro Yamaji; Shohei Kodama; Yuji Ohashi; Yuui Yokota; Kei Kamada; Akira Yoshikawa; Akimasa Ohnishi; Mamoru Kitaura
IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 巻：65, 号：8, 開始ページ：2136, 終了ページ：2139, 2018年08月
Ce-doped (Gd,La)(2)Si2O7 (Ce:La-GPS) scintillator was found to have a good light output of around 40000 photons/MeV, while some other parameters have not been determined so far. In order to clarify the cause for such a high light yield, some physical parameters have been estimated in this paper. The bandgap energy of Ce:La-GPS was evaluated to be over 7.13 +/- 0.03 eV for (Gd-0.75, La-0.25)(2)Si2O7. Although Ce:La-GPS had wider bandgap compared with the other oxide scintillators, its light output was larger than values for some other scintillators. Since quantum yield of Ce:La-GPS was as high as around 0.8, the product of transfer efficiency and electron-hole pair generation efficiency was estimated to be around 0.9, which was higher than for the other scintillators. Thus, Ce:La-GPS was suggested to have high the product of transfer efficiency and/or electron-hole pair generation efficiency.
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1109/TNS.2018.2841917
DOI ID：10.1109/TNS.2018.2841917, ISSN：0018-9499, eISSN：1558-1578, Web of Science ID：WOS:000442365000026 - Growth and luminescent properties of Ce and Eu doped Cesium Hafnium Iodide single crystalline scintillators
Shohei Kodama; Shunsuke Kurosawa; Akihiro Yamaji; Jan Pejchal; Robert Kral; Yuji Ohashi; Kei Kamada; Yuui Yokota; Martin Nikl; Akira Yoshikawa
JOURNAL OF CRYSTAL GROWTH, 巻：492, 開始ページ：1, 終了ページ：5, 2018年06月
In order to obtain new scintillators with high light output and high effective atomic number (Z(eff)), we performed anion-substitution for Cs2HfCl6 (CHC) scintillator, and then, we succeeded in growing Cs2HfI6 (CHI) single crystalline scintillator. It had Z(e)n of 58, which is the same as that of CHC, and had high light output of similar to 70,000 photons/MeV with 700 nm emission. However, its scintillation decay time of similar to 2.5 mu s was slow for practical use as gamma-ray monitor. In this study, we performed Ce3+/Eu2+ doping to Hf4+ site to improve decay time of CHI, introducing the fast 5d-4f luminescence. Ce:CHI and Eu:CHI single crystals were finally obtained by the vertical Bridgman-Stockbarger method. The luminescence spectra of the Ce:CHI and Eu:CHI were very similar to that of the non-doped CHI, which would mean that no 5d-4f luminescence of Ce3+/Eu2+ was observed. The measured light output and decay time of Ce:CHI were similar to 48,000 photon/MeV and 2.3 +/- 0.1 mu s, respectively. As for Eu:CHI, light output and decay time were similar to 69,000 photon/MeV and 2.8 +/- 0.1 mu s, respectively. (C) 2018 Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
DOI：https://doi.org/10.1016/j.jcrysgro.2018.03.033
DOI ID：10.1016/j.jcrysgro.2018.03.033, ISSN：0022-0248, eISSN：1873-5002, Web of Science ID：WOS:000432747200001
- コバルト60ガンマ線照射装置を使ったシンチレータ評価とその応用
黒澤俊介; 黒澤俊介; 黒澤俊介; 田中浩基; 高田卓志; 松倉大佑; 松倉大佑; 浦野雄介; 浦野雄介; 藤原千隼; 藤原千隼; 山路晃広; 山路晃広; 小玉翔平
KURNS-EKR (Web), 号：19, 2024年
ISSN：2434-1088, J-Global ID：202402219494722076 - 近赤外発光を示すヨウ化物蛍光体の開発
黒澤俊介; 黒澤俊介; 松倉大佑; 浦野雄介; 山路晃広; 吉川彰; 藤原千年; 小玉翔平
Journal of Flux Growth, 巻：17, 号：2, 2023年
ISSN：1881-5316, J-Global ID：202402287440244736 - 廃炉作業におけるガンマ線検出に向けたNd添加Y3Al5O12シンチレータの開発
松倉大佑; 松倉大佑; 黒澤俊介; 黒澤俊介; 黒澤俊介; KOCHURIKHIN Vladimir; 小玉翔平; 藤原千隼; 藤原千隼; 山路晃広; 山路晃広; 大橋雄二; 大橋雄二; 横田有為; 鎌田圭; 鎌田圭; 佐藤浩樹; 佐藤浩樹; 豊田智史; 豊田智史; 吉野将生; 吉野将生; 花田貴; 村上力輝斗; 堀合毅彦; 堀合毅彦; 吉川彰; 吉川彰; 吉川彰
応用物理学会秋季学術講演会講演予稿集(CD-ROM), 巻：83rd, 2022年
ISSN：2758-4704, J-Global ID：202302239156460577
- 赤色発光シンチレータCs2HfI6単結晶の大型化に向けた条件探索
小玉 翔平; 大宮 昇悟; 黒澤 俊介; 吉野 将生; 柳瀬 郁夫; 武田 博明
第72回応用物理学会春季学術講演会, 2025年03月
2025年03月 - 2025年03月, 口頭発表（一般） - Flux growth of oxide scintillators for neutron detection
Shohei Kodama; Taiga Nishii; Miki Sodeno; Shunsuke Kurosawa; Akira Yoshikawa; Ikuo Yanase; Hiroaki Takeda
17th International Conference on Scintillating Materials and their Applications (SCINT2024), 2024年07月, ［招待有り］
2024年07月 - 2024年07月, 口頭発表（招待・特別） - Recent development of fast red/NIR oxide phosphors doped with Eu2+
Shohei Kodama; Tomoki Saito; Ikuo Yanase; Hiroaki Takeda
The 8th International Workshop on Advanced Spectroscopy and Optical Materials (IWASOM2024), 2024年07月, ［招待有り］
2024年07月 - 2024年07月, 口頭発表（招待・特別）
- 新シンチレータ材料開発で目指すリアルタイム遠隔α-γ-n弁別線量モニタの実現
日本学術振興会, 科学研究費助成事業, 基盤研究(B), 2024年04月 - 2028年03月
小玉 翔平; 武田 博明; 柳瀬 郁夫, 埼玉大学
配分額（総額）：18590000, 配分額（直接経費）：14300000, 配分額（間接経費）：4290000
課題番号：24K01397 - ケイ酸塩系新圧電結晶の結晶構造に基づく材料設計と高温振動子の開発
日本学術振興会, 科学研究費助成事業, 基盤研究(B), 2022年04月01日 - 2026年03月31日
武田 博明; 柳瀬 郁夫; 小玉 翔平; 青柳 忍, 埼玉大学
配分額（総額）：17290000, 配分額（直接経費）：13300000, 配分額（間接経費）：3990000
課題番号：22H02162 - 協奏的マルチプローブ分光による不純物共賦活シンチレータの特性改善の学理究明
日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2022年04月01日 - 2025年03月31日
北浦 守; 鎌田 圭; 小玉 翔平, 山形大学
配分額（総額）：4160000, 配分額（直接経費）：3200000, 配分額（間接経費）：960000
課題番号：22K04681 - 高品質単結晶育成で目指す超高発光量・赤色発光ヨウ化物シンチレータの開発
日本学術振興会, 科学研究費助成事業, 若手研究, 2022年04月01日 - 2025年03月31日
小玉 翔平, 埼玉大学
配分額（総額）：4550000, 配分額（直接経費）：3500000, 配分額（間接経費）：1050000
課題番号：22K14611 - 層状構造等をもつセラミックスを用いた空気中二酸化炭素の室温高速吸収無機固体の創成
日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2021年04月01日 - 2024年03月31日
柳瀬 郁夫; 武田 博明; 小玉 翔平, 埼玉大学
配分額（総額）：4160000, 配分額（直接経費）：3200000, 配分額（間接経費）：960000
課題番号：21K05222 - 自己発光ハロゲン化物シンチレータの発光メカニズム仮説の実験的検証
日本学術振興会, 科学研究費助成事業, 研究活動スタート支援, 2021年08月30日 - 2023年03月31日
小玉 翔平, 埼玉大学
配分額（総額）：3120000, 配分額（直接経費）：2400000, 配分額（間接経費）：720000
本研究の目的は、自己発光ハロゲン化物シンチレータA2BX6（A:アルカリ金属元素、B:4価金属元素、X:ハロゲン元素）の発光メカニズムを実験的に明らかにすることである。A2BX6の中には、2015年に米国で報告された青色発光Cs2HfCl6や、代表者が単結晶育成に成功した赤色発光Cs2HfI6・Rb2HfI6などがあり、いずれも40,000光子/MeVを超える高い発光量と良好なエネルギー分解能を有するシンチレータとして注目を集めている。しかしその発光メカニズムは、いくつかのモデルがシミュレーションによって提案されているものの未決定である。理論に基づいて効率よく性能改善を行うためには、発光メカニズムの解明が必要である。そこで本研究では、いくつかのA2BX6型ハロゲン化物を実際に合成し、構成元素と発光の有無を調査することで、発光メカニズムの実験的な決定を目指す。
2021年度は、まず着任研究室におけるハロゲン化物合成環境の立ち上げから取り組んだ。真空型小型グローブボックスをはじめとする真空部品・ポンプ等の必要物品を購入し、セットアップを行った。また、ハロゲン化物用石英ガラスアンプルの素形材として、石英ガラス素管を購入し、ガラス加工を行い、合成の基本的な環境を整えた。塩化物原料粉末を購入し、所属研究室が現有していた粉末と混合し、ハロゲン化物の合成テストとしてCs2ZrCl6を焼成した。焼成したサンプルをシンクロトロン施設に持ち込んで極低温発光スペクトルを測定したところ、室温付近ではHfと同様に発光が見られ、室温で見えていた発光が150K以下で大きく強度が上がることが分かった。
課題番号：21K20550 - 水晶を凌駕する新規圧電材料・デバイスの開発
日本学術振興会, 科学研究費助成事業, 基盤研究(B), 2019年04月01日 - 2022年03月31日
武田 博明; 柳瀬 郁夫; 青柳 忍; 西田 貴司; 小玉 翔平; 鶴見 敬章; 保科 拓也, 埼玉大学
配分額（総額）：17420000, 配分額（直接経費）：13400000, 配分額（間接経費）：4020000
本研究は水晶では対応できない1000℃まで使用可能な新規圧電結晶を創製し，その各種圧電センサを開発することを目的とした．燃焼圧センサとして一部実用化されているランガサイト型結晶，本研究者らが見いだしたメリライト型結晶に注目し，両結晶が抱えている課題の解決を試みた．ランガサイト型結晶では異常燃焼時による結晶の破壊を防ぐため，熱応力の異方性を抑えた新規結晶を開発した．メリライト型結晶では結晶構造と圧電特性の関係の解明することで，低い機械的強度を克服できる新規結晶を開発した．後者のメリライト型結晶は水晶を凌駕する新しい高温用圧電材料となりえることが明らかとなった．
課題番号：19H02797 - 高速発光を有するハフニウム含有ハロゲン化物シンチレータの創製とその発光機構の解明
日本学術振興会, 科学研究費助成事業, 特別研究員奨励費, 2018年04月25日 - 2021年03月31日
小玉 翔平, 東北大学
配分額（総額）：3100000, 配分額（直接経費）：3100000
本研究は発光量・エネルギー分解能に優れるが蛍光寿命が遅く用途が限られている新規ハロゲン化物シンチレータCs2HfCl6の特性向上、特に蛍光寿命の高速化を目指している。2018年度までで、蛍光寿命がCs2HfCl6の約半分となるヨウ化物シンチレータCs2HfI6（CHI）の開発に成功しており、かつ、CHIはこれまで実現されてこなかった赤色領域で高発光量を示すシンチレータとなった。そこで2019年度は、目標の特性を有する新規シンチレータの開発のため、ハロゲン置換による蛍光寿命の高速化を目指して研究を行った。加えて、開発したCHIの実用化に向けて、赤色発光の利点を強く活かした画期的なリモート放射線量モニタの試作・実働試験を行った。
Cs2HfX6（XはCl, Br, I）の組成からなる種々のハロゲン混合単結晶を育成し、発光・放射線応答特性を評価した。構成ハロゲンをClからBr、Iへと変えてゆくと発光波長が長波長へとシフトしてゆき、Iが含まれる結晶の発光波長はCs2HfI6同様に700 nm付近となった。青～黄色領域で発光する塩臭化物の蛍光寿命は測定可能であり、Cs2HfCl3Br3は2.18 ± 0.27 μsとなり、塩臭化物もCs2HfCl6よりも早い蛍光寿命を有することが分かった。一方、既存の光電子増倍管は700 nm付近の量子効率が著しく悪く、蛍光寿命を精度よく測定することができなかった。そのため、測定戒能にするための新しい測定環境を現在立ち上げ中である。また、Cs2HfCl3Br3単結晶を用いて単結晶X線回折による結晶構造解析を行ったところ、ClとBrはHfに対してランダムに配位した[HfCl3Br3]八面体を形成していることが分かった。
課題番号：18J21316