| White light-emitting diode (W-LED), as a novel kind of'green lighting', has many advantages over incadescent and fluorescent lamps, such as low working voltage, low power consumption, high luminous efficiency and long life. Therefore, W-LED and related phosphors have attracted worldwide attention. In this Master Thesis, we focus our research on blue-emitting phosphors that can be excited by long-wave ultraviolet or violet LED chips and will have practical applications in W-LED.We review in the first part of thesis the present situation and future trends of W-LED and blue-emitting phosphors, with emphasis placed on the mechanism of W-LED, various kinds of phosphors and various preparation methods. For the demand of high color rendering W-LED, we chose (SrCaBa)3(PO4)2·SrCl2:Eu2+ blue-emitting phosphor powder as the object of our study, and use high-temperature solid-state reaction method to prepare the phosphor powders in a weak reducing atmosphere. A detailed investigation on the reaction parameters, including kinds and relative ratio of raw materials, sintering temperature and Eu2+ activator concentration was conducted in terms of luminescent properties of phosphors powder. Our study show that optimal reaction parameters are: sintering temperature is 1200℃, Eu2+ doping level is 0.15. By these parameters, the (SrCaBa)3(PO4)2·SrCl2:Eu2+ phosphor powder show bright blue emission around 450nm and can be efficiently excited by violet and ultraviolet light (200nm- 440nm).Further we employed the energy transfer between Tb3+ and Eu2+ and prepared a novel series of phosphors using (SrCaBa)3(PO4)2·SrCl2 as host material. Our study show that emission color can be adjusted from blue to blue green by the ratio of Tb3+ to Eu2+, with line-like Tb3+ green emission overlapped on band-like Eu2+ blue emission. This novel series of phosphors may have promising applications in high-color-rendering W-LED. |
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