Research On The Fluorescent Glass For White Led

In recent years, the consumed electricity is increasing with the development ofilluminated light source, which runs counter to energy conservation. And there areenvironmentally harmful substances in the traditional illumination light source. Dueto the advantages of environmentally friendly, low energy consumption, good colorrendering, long lifetime, fast response, etc., white LED has received extensiveattention. Currently the most important method to achieve white LED is acombination of the blue LED and yellow-emitting phosphors doped with rare earthions. However, this method has many defects, such as lack of red component, poorthermal stability, easy aging, etc. Therefore, fluorescent glass doped with rare earthions is used to obtain white light in this paper. Compared with traditional phosphors,fluorescent glass has more advantages in terms of thermal stability, luminousuniformity and preparation technology, etc.In this paper, the conventional melt quenching technology was used to preparethe borosilicate fluorescent glasses (SiO2-B2O3-CaO) which were single-doped orco-doped with Ce3+, Dy3+and Eu3+. The fluorescent glasses were characterized withexcitation spectrum, emission spectrum, chromaticity diagram, chromaticitycoordinates and color temperature. The effect of the concentration of rare earth ionson the intensity and effectiveness of white light emitted from fluorescent glass canbe learned and the optimal concentration of rare earth ions can be obtained. Inaddition, the energy level transition and energy transfer between rare earth ions havebeen also studied.(1) The conventional melt quenching technology was used to prepare theborosilicate fluorescent glasses co-doped with Ce3+and Dy3+. Firstly, in order toobtain the optimum doped ratio of Ce3+and Dy3+, the sum concentrations of the tworare earth ions remain unchanged and their respective concentration was graduallyvaried. Excited with UV of363nm, the fluorescent glasses will emit blue and yellowlight which can synthesize white light. When the concentration radio of Ce3+andDy3+is1:6, the best white light can be obtained whose chromaticity coordinate is(0.3262,0.3345) and color temperature is6000K. Then in order to obtain theoptimum doped concentration of Ce3+and Dy3+, the concentration of the two rareearth ions is gradually changed while the optimum ratio was kept constant. Bycalculated and analyzed, the fluorescent glasses co-doped with0.15mol%CeO2and0.45mol%Dy2O3can emit white light with the strongest intensity whosechromaticity coordinate is (0.3250,0.3377) and color temperature is6000K. Thisresult is consistent with the one of the concentration radio of Ce3+and Dy3+is1:6. (2) Due to the lack of red component, the color temperature of synthesizedwhite light above is high. Therefore, different concentrations of Eu2O3were dopedin the fluorescent glasses to adjust the color temperature. By calculated andanalyzed, the fluorescent glass tri-doped with0.15mol%CeO2,0.45mol%Dy2O3and0.03%Eu2O3can emit the best white light. Its chromaticity coordinate is(0.3334,0.3409) and color temperature is5500K, which is consistent with the one ofthe midday summer sun. When the concentration of Eu2O3is less or greater than0.03mol%, the synthesized light will be changed into cool or warm white light,respectively.(3) The conventional melt quenching technology was used to prepare theborosilicate fluorescent glasses co-doped with Ce3+/Dy3+, Ce3+/Eu3+and Dy3+/Eu3+,respectively. In order to verify the presence of the energy transfer between rare earthions, the concentration of one rare earth ion is maintained constant, and the otherone is changed. The emission spectrum can show the energy transfer from Ce3+toDy3+, Ce3+to Eu3+and Dy3+to Eu3+, respectively.