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pp.351-356
A spherical Sr4Al14O25:Eu2+ phosphor for use in white-light-emitting diodes was synthesized using a liquid-state reaction with two precipitation stages. For the formation of phosphor from a precursor, the calcination temperature was 1,100˚C. The particle morphology of the phosphor was changed by controlling the processing conditions. The synthesized phosphor particles were spherical with a narrow size-distribution and had mono-dispersity. Upon excitation at 395 nm, the phosphor exhibited an emission band centered at 497 nm, corresponding to the 4f65d→4f7 electronic transitions of Eu2+. The critical quenching-concentration of Eu2+ in the synthesized Sr4Al14O25:Eu2+ phosphor was 5 mol%. A phosphor-converted LED was fabricated by the combination of the optimized spherical phosphor and a near-UV 390 nm LED chip. When this pc-LED was operated under various forward-bias currents at room temperature, the pc-LED exhibited a bright blue-green emission band, and high color-stability against changes in input power. Accordingly, the prepared spherical phosphor appears to be an excellent candidate for white LED applications.
