Papers - OKA Ryohei

Preparation of Ca₂MnO₄ Films Using Bayesian Optimization and Their Black Color Properties Owing to Ti⁴⁺-Doping Reviewed

Ryohei Oka, Tomokatsu Hayakawa

Chemistry Letters   53 ( 12 )   upae221   2024.12

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/chemle/upae221

Control of Optical Reflection in Ca₂MgWO₆ by Co and Mo doping Reviewed

Kazuki Yamaguchi, Kohei Minagawa, Ryohei Oka, Toshiyuki Masui

Molecules   29 ( 8 )   1886   2024.04

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/molecules29081886

Tuning the Luminescence Color of Eu³⁺- and Alkali-Ion-Codoped Sr₂CaWO₆ Orange-Red Phosphors: Eu³⁺ Site Distribution and Site-Selective Photoluminescence Studies Reviewed International coauthorship

Takahito Otsuka, Ryohei Oka, Rita Maria Cicconi, Dominique de Ligny, Tomokatsu Hayakawa

APL Materials   12 ( 3 )   031129   2024.03

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0197892

Inorganic Green Pigments Based on LaSr₂AlO₅ Reviewed

Kazuki Yamaguchi, Akari Takemura, Saki Furumoto, Ryohei Oka, Toshiyuki Masui

Ceramics   6 ( 4 )   2269 - 2281   2023.11

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/ceramics6040138

Photoluminescence Color Prediction for Eu³⁺-doped Perovskite Red Phosphors using Machine Learning Reviewed

Takahito Otsuka, Ryohei Oka, Masayuki Karasuyama, Tomokatsu Hayakawa

Physica Status Solidi-Rapid Research Letters   18 ( 9 )   2300237   2023.09

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/pssr.202300237

Bandgap and Photoluminescence Tunability of Lead-Free Cs₃Bi₂(Br,I)₉ Solid Solution Compounds Reviewed International coauthorship

Haruto Hashimoto, Ryohei Oka, Tomokatsu Hayakawa, Christoph Brabec

Physica Status Solidi-Rapid Research Letters   18 ( 9 )   2300241   2023.09

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/pssr.202300241

Color Controllable Inorganic Pigments with Ce³⁺ as a Color Source Reviewed

Kazuki Yamaguchi, Yusuke Shobu, Ryohei Oka, Toshiyuki Masui

Inorganic Chemistry   62 ( 38 )   15392 - 15402   2023.09

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.inorgchem.3c01292

Eu³⁺ Site Distribution and Local Distortion of Photoluminescent Ca₃WO₆:(Eu³⁺, K⁺) Double Perovskites as High-Color-Purity Red Phosphors Reviewed

Takahito Otsuka, Ryohei Oka, Tomokatsu Hayakawa

Advanced Science   10 ( 31 )   2302559   2023.09

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/advs.202302559

Local Structural Investigation of Near-Infrared-Reflective Black Ca₂(Mn,Ti)O₄ Pigments Using Synchrotron Radiation X-ray and Density Functional Theory Calculations Reviewed

Ryohei Oka, Tomokatsu Hayakawa

Inorganic Chemistry   62 ( 36 )   14647 - 14658   2023.08

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.inorgchem.3c01897

Synthesis of Calcium Manganese Oxide Films Using a Sol-Gel Method and Evaluation of Color and Photocatalytic Properties Reviewed

Ryohei Oka, Tomokatsu Hayakawa

Physica Status Solidi-Rapid Research Letters   18 ( 9 )   2300233   2023.07

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/pssr.202300233

Nd-Doped NASICON-Type Nanophosphors for Near-Infrared Excitation and Emission Reviewed

Mizuki Watanabe, Masahiro Itoh, Ryohei Oka, Shintaro Ida, Toshiyuki Masui

Journal of Asian Ceramic Societies   11 ( 2 )   239 - 249   2023.03

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/21870764.2023.2186842

A Novel Inorganic Violet Pigment Based on Zinc Niobate Reviewed

Kazuki Ohnishi, Ryohei Oka, Yuga Nomura, Toshiyuki Masui

Materials Advances   4 ( 6 )   1583 - 1589   2023.03

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d3ma00040k

Introduction to the annual S&T poster for everyone, titled “Glass ­ One S&T poster for Every Household” and its related activities Reviewed

Madoka Ono, Kenji Shinozaki, Jumpei Ueda, Ryohei Oka, Tetsuo Kishi, Sunao Kurimura, Yoshihiro Takahashi, Tomoharu Hasegawa, Yoshimasa Matsushita, Takahiro Murata, Yoshiki Yamazaki

Journal of the Ceramic Society of Japan   130 ( 8 )   509 - 511   2022.08

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2109/jcersj2.22066

Synthesis and Color Evaluation of Tb⁴⁺-Doped Na₂ZrO₃ for Inorganic Yellow Pigments Reviewed

Ryohei Oka, Tomoyo Nouchi, Toshiyuki Masui

Colorants   1 ( 3 )   347 - 353   2022.08

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/colorants1030020

Novel Near-Infrared Reflective Black Inorganic Pigment Based on Cerium Vanadate Reviewed International journal

Takuro Morimoto, Ryohei Oka, Kohei Minagawa, Toshiyuki Masui

RSC Advances   12 ( 26 )   16570 - 16575   2022.06

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/d2ra02483g

Raman Spectroscopic Investigation and Electronic States Calculation for Ca₂(Mn,Ti)O₄ Black Pigments with High Near-Infrared (NIR) reflectivity Reviewed International journal

Ryohei Oka, Tomokatsu Hayakawa

Inorganic Chemistry   61 ( 17 )   6500 - 6507   2022.04

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/acs.inorgchem.2c00254

Novel Findings on Optical Properties of Mn⁴⁺-Doped (Rb,K)₂Ge₄O₉ Phosphors Reviewed International journal

Ryohei Oka, Daiki Nishi, Tomokatsu Hayakawa

Physica Status Solidi B   259 ( 9 )   2100615   2022.02

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/pssb.202100615

Novel Inorganic Orange Pigments Based on BiFeWO₆ Reviewed

Ryohei Oka, Akari Takemura, Yusuke Shobu, Kohei Minagawa, Toshiyuki Masui

Journal of the Ceramic Society of Japan   130 ( 1 )   39 - 43   2022.01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Ceramic Society of Japan  

DOI： 10.2109/jcersj2.130.P1-1

Novel Orange Color Pigments Based on La₃LiMnO₇ Reviewed

Ryohei Oka, Jun-ichi Koyama, Takuro Morimoto, Toshiyuki Masui

Molecules   26 ( 20 )   6243   2021.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

DOI： 10.3390/molecules26206243

Studies on Novel Environment-Friendly Inorganic Pigments Reviewed

Ryohei Oka

2021.03

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Language：English   Publishing type：Doctoral thesis  

Synthesis and Characterization of Ca_1−xEu_xZrO₃ as Environmentally Friendly Inorganic Yellow Pigments Reviewed International journal

Kohei Minagawa, Yuichi Nishiguchi, Ryohei Oka, Toshiyuki Masui

ACS Omega   6 ( 4 )   3411 - 3417   2021.01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/acsomega.0c05959

Effect of [MnO₆] Octahedra to the Coloring Mechanism of (Li_1−xNa_x)₂MnO₃ Reviewed International journal

Ryohei Oka, Kohei Kusukami, Toshiyuki Masui

ACS Omega   5 ( 22 )   13108 - 13114   2020.05

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/acsomega.0c01071

Improvement of Near-infrared (NIR) Reflectivity and Black Color Tone by Doping Zn²⁺ into the Ca₂Mn_0.85Ti_0.15O₄ Structure Reviewed International journal

Ryohei Oka, Senri Iwasaki, Toshiyuki Masui

RSC Advances   9 ( 66 )   38822 - 38827   2019.11

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/c9ra07849e

Submicron-Sized Phosphors Based on Hexagonal Rare Earth Oxycarbonate for Near-infrared Excitation and Emission Reviewed International journal

Mizuki Watanabe, Yasuhiro Sejima, Ryohei Oka, Shintaro Ida, Toshiyuki Masui

Journal of Asian Ceramic Societies   7 ( 4 )   502 - 508   2019.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Group  

DOI： 10.1080/21870764.2019.1673137

Enhancement of Near-infrared Emission of Neodymium-Doped Monoclinic Gadolinium Phosphate Nanophosphors by Surface Coating with Calcium Phosphate Reviewed International journal

Mizuki Watanabe, Norifumi Yamamoto, Tomoaki Matsuo, Ryohei Oka, Shintaro Ida, Toshiyuki Masui

Journal of Asian Ceramic Societies   7 ( 4 )   509 - 517   2019.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Group  

DOI： 10.1080/21870764.2019.1673138

Synthesis and Color Evaluation of Ta⁵⁺-Doped Bi₂O₃ Reviewed International journal

Ryohei Oka, Yusuke Shobu, Toshiyuki Masui

ACS Omega   4 ( 4 )   7581 - 7585   2019.04

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

DOI： 10.1021/acsomega.9b00555

Novel Environmentally Friendly Inorganic Orange Pigments Based on Ca₁₄Al₁₀Zn₆O₃₅ Reviewed

Ryohei Oka, Takashi Kosaya, Toshiyuki Masui

Chemistry Letters   47 ( 12 )   1522 - 1525   2018.10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/cl.180744

Synthesis and Characterisation of Ba(Zn_1−xCo_x)₂Si₂O₇ (0 ≤ x ≤ 0.50) for Blue-violet Inorganic Pigments Reviewed International journal

Takashi Tsukimori, Yusuke Shobu, Ryohei Oka, Toshiyuki Msaui

RSC Advances   8 ( 16 )   9017 - 9022   2018.02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/c8ra00101d

Synthesis and Characterisation of SrY_2−xCe_xO₄ as Environmentally Friendly Reddish-brown Pigments Reviewed International journal

Ryohei Oka, Yusuke Shobu, Fumiya Aoyama, Takashi Tsukimori, Toshiyuki Masui

RSC Advances   7 ( 87 )   55081 - 55087   2017.12

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/c7ra10250j

Perovskite-type ALnO₃ (A = Ca, Sr, Ba; Ln = Ce, Pr, Tb) Oxides as Environmentally Friendly Yellow Pigments Reviewed

Ryohei Oka, Takashi Tsukimori, Hiroki Inoue, Toshiyuki Masui

Journal of the Ceramic Society of Japan   125 ( 8 )   652 - 656   2017.08

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Ceramic Society of Japan  

DOI： 10.2109/jcersj2.17118

Synthesis and Characterization of Bi₄Zr₃O₁₂ as an Environment-friendly Inorganic Yellow Pigment Reviewed International journal

Takashi Tsukimori, Ryohei Oka, Toshiyuki Masui

Dyes and Pigments   139   808 - 811   2017.01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

DOI： 10.1016/j.dyepig.2017.01.013

Synthesis and Characterization of Black Pigments Based on Calcium Manganese Oxides for High Near-infrared (NIR) Reflectance Reviewed International journal

Ryohei Oka, Toshiyuki Masui

RSC Advances   6 ( 93 )   90952 - 90957   2016.09

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/c6ra21443f