The Fabrication And Study Of Luminescent Glass-ceramic For Blue LED

Yellow YAG:Ce phosphor is a critical materials in the fabrication of white LED, and the research of the YAG:Ce phosphor has an important practical significance and application prospects. In this paper, rare earth (Ce3+,Gd3+) doped YAG glass-ceramic was fabricated by high temperature solid state method in the weak reducing atmosphere, which has the potential to replace the traditional WLED with a phosphor and resin packaging process. The glass matrix is based on the yttrium aluminum garnet system, adding a certain amount of glass-forming body, nucleating agent, alkaline earth metal and rare earth ions. The crystallization behavior and luminescent properties of the Re3+(Ce3+,Gd3+) doped glass-ceramics were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM),Fluorescence Spectra and CIE.The results indicate that:We can obtain the Ce3+doped YAG glass-ceramics after heat treatment. The glass ceramics have single YAG phase, and the phase is in uniform distribution state with a diameter between 80-120nm. And the as-made glass-ceramics can be effectively excited by the blue LED chips at 450nm～470nm, emitting yellow fluorescence, which attributes to the 4fâ†'5d transitions of Ce3+, and produce white light after complexion with the blue fluorescence from the blue LED chips. Yttrium aluminum garnet matrix glass can be easily crystallized, which means that it can precipitate a single phase without adding any nucleating agents, and the main crystal phase won't be affected by increasing the heating time. The ratio of the Al2O3/Y2O3 has a great impact on the luminescent properties, and the result shows the best luminescent properties of glass-ceramic when Al2O3/Y2O3=1.5. With increasing the concentration of Ce3+-doped, the luminescent intensity is enhanced, but when it reaches certain saturation, the more you dope the lower intensity you will get. The excitation and emission spectra of Gd3+ and Ce3+ co-doped YAG glass ceramic are similar with shape of Ce3+ single-doped one. The doped of Gd2O3 does not change the crystal structure of YAG, but the band gap of YAG will reduce, which makes the emission spectrum of Ce3+ produce a red shift, and decreases the light intensity.