• Kyu-Seog Hwang

      Articles written in Bulletin of Materials Science

    • Cost-effective electrostatic-sprayed SrAl2O4:Eu2+ phosphor coatings by using salted sol–gel derived solution

      Kyu-Seog Hwang Bo-An Kang Sung-Dai Kim Seung Hwangbo Jim-Tae Kim

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      3 Mol% of europium doped strontium aluminate (SrAl2O4:Eu2+) coatings on silicon substrates were prepared by electrostatic spray deposition method using a salted sol–gel derived solution as a starting material. Asdeposited films at 100°C for 5 h were heated at 1100°C for 2 h under a reducing ambient atmosphere of 95%N2 + 5%H2 . Nanocrystalline SrAl2O4 film was confirmed by surface morphological and crystallographic analyses. Monitored at 520 nm, the excitation spectrum showed a broad band from 300 ∼ 500 nm and the emission intensity showed a maximum yellow peak intensity at 512 nm with a broad band from 460 ∼ 610 nm.

    • Red-emitting alkaline-earth rare-earth pentaoxometallates powders prepared by metal carboxylates solution

      Kyu-Seog Hwang Sung-Dae Kim Seung Hwangbo Jin-Tae Kim

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      Moisture-insensitive metal carboxylates that are mostly liquids at room temperature have been first applied to the preparation of strontium europium aluminate (Sr2EuAlO5) powders for red-emitting phosphor under near ultraviolet radiation. Strontium naphthenate, aluminium-2-ethylhexanoate and europium-2-ethylhexanoate were dissolved with toluene to prepare starting solution. Precursor pyrolyzed at 500 °C for 240 min was finally annealed at 900–1200 °C for 240 min in Ar. X-ray diffraction analysis, field emission–scanning electron microscope and fluorescent spectrophotometer were used to evaluate structural and optical properties. For the 1000 °C-annealed powders with regular shape and narrow size distribution confirmed by FE–SEM observation, strong red emission at 615nm under the excitation of 395nm maximum was reached, then the higher annealed samples at above 1100 °C gave the lower emission intensities.

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