Luminescence properties of (Sr1-uBau)Si2O2N2:Eu2+, yellow or orange phosphors for white LEDs, synthesized with (Sr1-uBau)2SiO4:Eu2+ as a precursor

Luminescence properties and formation process of (Sr1-uBau)Si2O2N2:Eu2+, phosphors suitable for white light-emmitting (LEDs), were investigated. These phosphors were synthesized by a method using (Sr1-uBau)(2)SiO4:Eu2+ as a precursor instead of simple oxides. Compared with a conventional solid-state reaction method, this method provides increased luminescence efficiency. X-ray diffraction analysis has indicated that transformation of low-temperature type (Sr1-uBau)Si2O2N2:Eu2+ to high-temperature type, which has a higher luminescence efficiency, occurs with a higher probability when (Sr1-uBau)(2)SiO4:Eu2+ is used as a precursor. Under 460 nm excitation, (Su(1-u)Ba(u))Si2O2N2: Eu2+ shows an emission band peaked at 550 - 590 nm for varied Ba fraction u. This series of materials shows the high integrated photoluminescence intensity at u = 0.25 - 0.75. Particularly, at u = 0.5, it shows the highest quantum output, which is about 1.2 times as high as that of the commercial yellow phosphor, (Y, Gd)(3)Al5O12: Ce3+, P46-Y3. The internal quantum efficiency is estimated to be about 80% for samples of u = 0.5 and 0.75. The high efficiency and small thermal quenching allow these materials to be applied to white LEDs. (c) 2007 The Electrochemical Society.