Papers by Author: Kyota Uheda

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Authors: Kyota Uheda
Abstract: Multiternary nitride and oxynitride compounds doped with rare earth ions, such as Eu2+ and Ce3+ have been enthusiastically applied as various phosphors to white LED. New red and green phosphors, CaAlSiN3:Eu and Ba3Si6O12N2:Eu, have been successfully synthesized, recently. The red phosphor has intense emission around 650 nm under two different irradiations at 405 and 455 nm from blue- and near UV-LED chips, respectively; while strong emission is observed around 520 nm from the green phosphor. Both phosphors also show small thermal quenching over the temperatures up to 150 °C. In addition, both LaSi3N5:Ce and La3Si8O4N11:Ce in lanthanum silicon nitride and oxynitride were examined as candidates for a blue phosphor in white LED with near UV-LED chip.
Authors: Masayoshi Mikami, Satoshi Shimooka, Kyota Uheda, Hiroyuki Imura, Naoto Kijima
Abstract: A new oxynitride, Ba3Si6O12N2, has been synthesized. The crystal structure has been successfully determined by close collaboration between experiment and first-principles calculation. This compound doped with Eu exhibits intense green photoluminescence with high color purity under near-ultraviolet to blue light excitation; in particular, it has much less thermal quenching than (Ba,Sr,Eu)2SiO4. Thus (Ba,Eu)3Si6O12N2 appears promising green phosphor for white LED backlight for display. The atomic/electronic structure is discussed in comparison with Ba3Si6O9N4, which could not become efficient phosphor by doping Eu due to strong thermal quenching at room temperature.
Authors: Kyota Uheda, M. Takahashi, H. Takizawa, Takeshi Endo, Masahiko Shimada
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