Korean Journal of Materials Research ISSN:1225-0562(Print) 2287-7258(Online) 한국재료학회지

Green BaSi₂O₂N₂:0.02Eu²⁺ phosphor is synthesized through a two-step solid state reaction method. The first firing is for crystallization, and the second firing is for reduction of Eu³⁺ into Eu²⁺ and growth of crystal grains. By thermal analysis, the three-time endothermic reaction is confirmed: pyrolysis reaction of BaCO3 at 900 ºC and phase transitions at 1,300 ºC and 1,400 ºC. By structural analysis, it is confirmed that single phase [BaSi₂O₂N₂] is obtained with Cmcm space group of orthorhombic structure. After the first firing the morphology is rod-like type and, after the second firing, the morphology becomes round. Our phosphor shows a green emission with a peak position of 495 nm and a peak width of 32 nm due to the 4f⁶5d¹→4f⁷ transition of Eu²⁺ ion. An LED package (chip size 5.6 x 3.0 mm) is fabricated with a mixture of our green BaSi₂O₂N₂, and yellow Y₃Al₅O12 and red Sr₂Si₅N₈ phosphors. The color rendering index (90) is higher than that of the mixture without our green phosphor (82), which indicates that this is an excellent green candidate for white LEDs with a deluxe color rendering index.