Journal of Powder Materials

Kyeong-Youl Jung

4 Articles

Effect of Solution Properties on Luminance Characteristics of YAG:Ce Phosphors Prepared by Spray Pyrolysis: You-Mi Lee, Tae-Won Kang, Kyeong-Youl Jung; J Korean Powder Metall Inst. 2012;19(3):220-225.; DOI: https://doi.org/10.4150/KPMI.2012.19.3.220

Abstract PDF: YAG:Ce yellow phosphor particles were synthesized by spray pyrolysis with changing the solution properties and their luminous properties, crystal structure, and morphological changes were studied by using PL measurement, XRD, and SEM analysis. It was clear that the solution properties significantly affected the crystal phase, crystallite size, the PL intensity, and the morphology of YAG:Ce particles. At low calcination temperature, the addition of urea only to the spray solution was helpful to form a pure YAG phase without any impurity phases, as the result, the highest luminescence intensity was achieved at the calcination temperature of 900°C. When the calcination temperatures were larger than 1300°C, however, the YAG particles prepared without any additive showed the highest luminescent intensity. Regardless of the solution conditions, the emission intensity of YAG:Ce particles prepared by spray pyrolysis showed a linear relation with the crystallite size. In terms of the morphology of YAG:Ce particles, the addition of both DCCA and NH_4OH to the spray solution was effective to prepare a spherical and dense structured YAG particles.

Effect of Al Precursor Type on Mesoporous Alumina Particles Prepared by Spray Pyrolysis: Joo-Hyun Kim, Kyeong-Youl Jung, Kyun-Young Park; J Korean Powder Metall Inst. 2010;17(3):209-215.; DOI: https://doi.org/10.4150/KPMI.2010.17.3.209

Abstract PDF: Mesoporous alumina particles were prepared by spray pyrolysis using cetyltrimethyl-ammonium bromide (CTAB) as a structure directing agent and the effect of Al precursor types on the texture properties was studied using N_2 adsorption isotherms, small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The surface area and the microstructure of alumina particles were significantly influenced by the Al precursor type. The largest BET surface area was obtained when Al chloride was used, whereas alumina particles prepared from Al acetate had the largest pore volume. According to small-angle X-ray scattering (SAXS) analysis, the alumina powders prepared using nitrate and acetate precursors had a clear single SAXS peak around 2theta=1.0sim1.5°, indicating that regular mesopores with sponge-like structure were produced. On the basis of TEM, SAXS, and N_2 isotherm results, the chloride precursor was most profitable to obtain the largest surface area (265;m2/g), whereas, the nitrate precursor is useful for the preparation of non-hollow mesoporous alumina with regular pore size, maintaining high surface area (sim233;m2/g).

Luminescent Properties of Y₂O₃:Eu Red Phosphor Particles Prepared by Microwave Synthesis: Meriel Chua Maniquiz, Tae-Won Kang, Jin-Han Ahn, Kyeong-Youl Jung; J Korean Powder Metall Inst. 2009;16(3):203-208.; DOI: https://doi.org/10.4150/KPMI.2009.16.3.203

Abstract PDF: Y_2O_3:Eu red phosphor was prepared by microwave synthesis. The crystal phase, particle morphology, and luminescent properties were characterized by XRD, SEM, and spectrofluorometer, respectively. The prepared Y_2O_3:Eu particles had good crystallinity and strong red emission under ultravioletet excitation. The crystallite size increased with calcination temperature and satuarated at 1200°C. The primary particle size initially formed was varied from 30 to 450 nm with microwave-irradiation (MI) time. It was found that the emission intensity of Y_2O_3:Eu phosphor strongly depends on the MI time. In terms of the emission intensity, it was recommended that the MI time should be less than 15 min. The emission intensity of Y_2O_3:Eu phosphor prepared by microwave syntehsis strongly depended on the crystallite size of which an optimal size range was 50-60 nm.

Optimization of VUV Characteristics of M₃MgSi₂O₈:Eu²⁺ (M=Ca, Sr, Ba) Phosphor by Spray Pyrolysis: You-Ri Jung, Kyeong-Youl Jung; J Korean Powder Metall Inst. 2008;15(5):399-404.; DOI: https://doi.org/10.4150/KPMI.2008.15.5.399

Abstract PDF: Spray pyrolysis was applied to prepare M_3MgSi_2O_8:Eu2+ (M=Ca, Sr, Ba) blue phosphor powder. The library of a Ca-Sr-Ba ternary system was obtained by a combinatorial method combined with the spray pyrolysis in order to optimize the luminescent property under vacuum ultraviolet (VUV) excitation. 10 potential compositions were chosen from the first screening. The emission shifted to longer wavelength as Ca became a dominant element and the emission intensity was greatly reduced in the composition region at which Ba is dominant element. On the base of the first screening result, the second fine tuning was carried out in order to optimize the luminescence intensity under VUV excitation. The optimal composition for the highest luminescence intensity was (Ca_1.7,;Sr_0.3,;Ba_1.0)Si_2O_8:Eu2+ which had the color coordinate of (0.152, 0.072) and about 64% emission intensity of BaMgAl_10O_17 (BAM) phosphor.

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