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Synthesis and photoluminescence properties of HEu(MoO4)2 nanophosphor
Mizuki Watanabe,Kazuyoshi Uematsu,김선욱,Kenji Toda,Mineo Sato 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.3
The HEu(MoO4)2 nanophosphor was synthesized for the first time by the H+ -exchange of KEu(MoO4)2. The nanophosphor obtained in the present study maintain the triclinic KEu(MoO4)2 type structure in a single phase form with high crystallinity. The HEu(MoO4)2 phosphor has rod-like particle morphology (length 0.5-20 µm, diameter 50-400 nm). Both HEu(MoO4)2 powder and solution shows red emission due to the 4f-4f transition of Eu3+.
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.
Novel yellowish white-emitting Eu2+-activated phosphate phosphor based on Rb2Ba3P4O14
Kazuma Sugimoto,Takuya Hasegawa,김선욱,Kazuyoshi Uematsu,Kenji Toda,Mineo Sato 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5
Eu2+-doped Rb2Ba3P4O14 phosphors were synthesized in a single phase form by a conventional solid state reaction method andtheir optical properties were characterized. These phosphors showed broad optical absorption bands that can cover the UVand near-UV region, and exhibited a narrow deep-blue emission and broad reddish-yellow emission with peaks at 423 nm and550 nm, respectively. The highest reddish-yellow emission intensity was obtained for Rb2(Ba0.99Eu0.01)3P4O14.
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+.
High thermal stable blue-emitting alkali silicate phosphor, Eu2+-activated Na2Mg2Si6O15
Masato Iwaki,Kazuma Sugimoto,Masaru Watanabe,Kazuyoshi Uematsu,Kenji Toda,Mineo Sato 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.3
White LEDs based on near ultraviolet LED and red/green/blue phosphors have been attracted in terms of outstanding colorrendering index. In particular, we focus on the blue emitting phosphors because the commercial BaMgAl10O17:Eu2+ needs hightemperature in order to be obtained. In this study, we succeeded in synthesizing Eu2+-activated Na2Mg2Si6O15 phosphors asa single phase by the conventional solid state reaction. Eu2+-doped Na2Mg2Si6O15 phosphors showed the broad blue emissionfrom 400-550 nm due to the 4f-5d allowed transition of Eu2+ under the ultraviolet light excitation. Moreover, the emissionintensity of Eu2+-activated Na2Mg2Si6O15 phosphor at high temperature kept about 85% at 423 K, which indicated the thermalstability of Na2Mg2Si6O15:Eu2+ was extremely higher than that of other Eu2+-activated silicate phosphors. Thus, Eu2+-activatedNa2Mg2Si6O15 phosphor is able to become the novel luminescent material for White LED based on the near-ultraviolet LED.
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.
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.
Improved luminescence properties of Na2TiSiO5 phosphor by the Ge4+ doping in the crystal lattice
Young Ji Park,Sun Woog Kim,Kazuma Sugimoto,Takuya Hasegawa,Koudai Tanima,Kazuyoshi Uematsu,Kenji Toda,Mineo Satod 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5
Rare earth free white emitting Na2TiSi1−xGexO5 phosphors were synthesized by a conventional solid-state reaction method, and the photoluminescence properties were characterized. The phosphors obtained in the present study showed broad bluish-white emission with a peak at 485 nm due to the charge transfer transition between O2− and Ti4+ and the emission peak intensity was effectively enhanced by the Ge4+ doping in the Na2TiSiO5 crystal lattice. The emission peak intensity of Na2TiSi0.5Ge0.5O5 was 1.35 times higher than that of Na2TiSiO5 and the CIE chromaticity coordinate values for the phosphor were x = 0.29 and y = 0.38.
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>