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A novel bluish green-emitting RbBaScSi3O9 : Eu2+ phosphor for white LEDs
Takeshi Abe,김선욱,Tadashi Ishigaki,Kazuyoshi Uematsu,Kenji Toda,Mineo Sato 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.3
A novel bluish green-emitting silicate phosphor, RbBaScSi3O9 : Eu2+, was synthesized by a conventional solid state reaction method. The RbBaScSi3O9 : Eu2+ phosphor can be excited by a near-UV and blue light irradiation and presents a bluish green band centered at 500 nm due to the allowed transition from 4f6 5d1 to 4f7 of Eu2+. The maximum emission peak intensity was obtained at the composition of RbBaScSi3O9 : 10 mol%Eu2+, and the emission intensity was 13% compared with that of the commercial YAG phosphor.
Synthesis of blue-emitting (K1−xNax)Mg4(PO4)3:Eu2+ phosphors
김선욱,Takuya Hasegawa,Tadashi Ishigaki,Kazuyoshi Uematsu,Mineo Sato,Kenji Toda 한국정보디스플레이학회 2014 Journal of information display Vol.15 No.2
Blue-emitting (K1−xNax)Mg4(PO4)3:Eu2+ phosphors were synthesized through a conventional solid-state reaction method, and their photoluminescence properties were characterized. These phosphors exhibited the typical emission band assigned to the transition from 4f65d1 to 4f7 of Eu2+, and the emission intensity was effectively enhanced by Na+-doping into the host lattice. The highest blue emission peak intensity was obtained for (K0.65Na0.35)Mg4(PO4)3:1 mol%Eu2+, where the relative emission peak intensity was 33% of that for the commercial blue-emitting BaMgAl10O17:10 mol%Eu2+ phosphor. In addition, these phosphors have excellent thermal stability in the temperature quenching effect.
Takeshi Abe,윤대호,김선욱,Tadashi Ishigaki,Kazuyoshi Uematsu,Mineo Sato,Takaki Masaki,Kenji Toda 한국정보디스플레이학회 2014 Journal of information display Vol.15 No.1
A yellow-emitting silicate phosphor, NaAlSiO4:Eu2+,was synthesized through a new reducing technique, using SiO powder as a silica source, during the preparation process. The addition of SiO powder as a silica source significantly enhanced the Eu2+ content, which led toan increase in the photoluminescence emission intensity of the NaAlSiO4:Eu2+ phosphor.The optimization of the composition resulted in obtaining themaximum emission intensityfor NaAlSiO4:7mol% Eu2+.
김선욱,Takuya Hasegawa,Hiroyuki Yumoto,Tadashi Ishigaki,Kazuyoshi Uematsu,Kenji Toda,Mineo Sato 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.3
Rare earth-free white emitting (Sr,Sn)(Zn,Mn)P2O7 phosphors were synthesized in a single phase form by a conventional solidstate reaction method and photoluminescent properties were characterized. These phosphors showed three broad band in emission spectra at 340, 440, and 690 nm, and the ratio of emission intensity between blue-green light and red light changes with Mn2+ content increasing because of energy transfer from Sn2+ to Mn2+. The emission color of the phosphors varied from blue-white to orange-white with the increase in the Mn2+ content and the emission color of the (Sr0.90Sn0.10)(Zn0.97Mn0.03)P2O7 phosphor was very close to white light.
Hasegawa, Takuya,Kim, Sun Woog,Ueda, Tadaharu,Ishigaki, Tadashi,Uematsu, Kazuyoshi,Takaba, Hiromitsu,Toda, Kenji,Sato, Mineo The Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.36
<▼1><P>A novel red emitting, Ce<SUP>3+</SUP>-activated Sr3Sc4O9 phosphor were discovered, and its luminescent properties were investigated.</P></▼1><▼2><P>Most conventional white light emitting diodes (white-LEDs) that are widely used as a new lighting system in next generation lights with Y3Al5O12:Ce<SUP>3+</SUP> (YAG:Ce<SUP>3+</SUP>)-based phosphors have a low colour rendering index (CRI) because the YAG:Ce<SUP>3+</SUP> phosphor shows a weak emission intensity in the red spectral region. Therefore, discovering a red-emitting phosphor with a high-efficiency is quite important to enhance the CRI of white-LEDs. In this study, we successfully discovered a novel, red-emitting Ce<SUP>3+</SUP>-activated Sr3Sc4O9 phosphor that can be excited by blue-light irradiation at 425 nm. A crystal structure of the host material was first determined by Rietveld refinement, which indicated that it should be isostructural with Ba3Ln4O9 (Ln = Sc, Y and Dy-Lu). As the Ce<SUP>3+</SUP> content increased, the X-ray diffraction patterns shifted to a lower angle, which suggested that the Ce<SUP>3+</SUP> ion could substitute Sc in the Sr3Sc4O9 host. Under UV and blue-light excitation, the Ce<SUP>3+</SUP>-activated Sr3Sc4O9 phosphor exhibited a broad emission band with a maximum peak at 620 nm, and its full width half maximum (FWHM) was 180 nm (4530 cm<SUP>−1</SUP>). The highest emission intensity was obtained for Sr3(Sc0.997Ce0.003)4O9, and the internal quantum efficiency of this phosphor under excitation at 425 nm was 53%. To the best of our knowledge, the emission band of the Ce<SUP>3+</SUP>-activated Sr3Sc4O9 phosphor is the longest wavelength for a reported Ce<SUP>3+</SUP>-activated oxide phosphor.</P></▼2>
Kim, Sun Woog,Toda, Kenji,Hasegawa, Takuya,Watanabe, Mizuki,Kaneko, Tatsuro,Toda, Ayano,Itadani, Atsushi,Sato, Mineo,Uematsu, Kazuyoshi,Ishigaki, Tadashi,Koide, Junko,Toda, Masako,Kudo, Yoshiaki,Masak American Scientific Publishers 2018 Science of advanced materials Vol.10 No.4
<P>Lithium orthophosphate Li3PO4 nanoparticles were synthesized through a water assisted solid state reaction (WASSR) method. The nanoparticles obtained in this study adopt a stable orthorhombic structure (beta-type), which is a low temperature phase, in a single phase with high crystallinity. The Li3PO4 nanoparticles have a granular particle morphology and the particle size is less than 50 nm.</P>
Novel Soft Chemical Synthesis Methods of Ceramic Materials
Toda, Kenji,Kim, Sun Woog,Hasegawa, Takuya,Watanabe, Mizuki,Kaneko, Tatsuro,Toda, Ayano,Itadani, Atsushi,Sato, Mineo,Uematsu, Kazuyoshi,Ishigaki, Tadashi,Koide, Junko,Toda, Masako,Kudo, Yoshiaki,Masak Trans Tech Publications, Ltd. 2016 Key Engineering Materials Vol.690 No.-
<P>We report novel soft chemical synthesis method, solid hydratethermal reaction (SHR) method as a new soft chemistry. This method is very simple and can synthesize the ceramic materials just by storing the mixture of raw materials added a small amount of water in a reactor at low temperature below 373 K. For example, nanosize YVO4 (under 100 nm in diameter) was obtained using the SHR method.</P>
Novel green Sr4ScAl3O10:Eu2+ phosphor prepared by the Melt Quenching Technique
Kenji Toda,Masato Iwaki,Minenori Katsu,Shin-nosuke Kamei,Sun Woog Kim,Takuya Hasegawa,Masaru Muto,Ryota Yamanashi,Tatsuya Sakamoto,Tadashi Ishigaki,Kazuyoshi Uematsu,Mineo Sato,Dae Ho Yoon 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.3
New green-emitting Sr4ScAl3O10:Eu2+ phosphor was prepared using a novel melt quenching synthesis method. The temperatureof raw materials irradiated with the strong light of the Xe arc-lamp was rose up to about 2273 K, followed by a sharp dropin the temperature after turn off the lamp. This method is a useful tool for rapid screening of novel phosphor materials.
Development of Water Assisted Solid State Reaction for the Ceramic Materials
Toda, Kenji,Kim, Sun Woog,Hasegawa, Takuya,Watanabe, Mizuki,Kaneko, Tatsuro,Toda, Ayano,Yamanashi, Ryota,Kumagai, Shota,Muto, Masaru,Itadani, Atsushi,Sato, Mineo,Uematsu, Kazuyoshi,Ishigaki, Tadashi,K Trans Tech Publications, Ltd. 2017 Key Engineering Materials Vol.751 No.-
<P>We report a novel soft chemical synthesis method, water assisted solid state reaction (WASSR) method. This method is very simple and can synthesize many ceramic materials just by storing or mixing raw materials added a small amount of water in a reactor at low temperature below 373 K. For example, well-crystalline SrMoO4 was obtained using the WASSR method.</P>