| Solid state lighting is considered as the fourth generation of green lightingsource which is possible to replace the conventional lamp. Since1996, whitelight-emitting diodes (WLED) have attracted wide attention owing to theirfavorable properties such as small size, low heat and long life-time. In thisdissertation, we have synthesized three kinds of phosphors (Sr,Ba)3SiO5:Eu2+,Li2SrSiO4:Eu2+,Ce3+and (Y,Gd)BO3:Sb3+/Eu3+/Tb3+which suited to different LEDchips. Moreover, the structure, morphology and luminescence properties of thesephosphors have been characterized by X-ray diffraction, scanning electronmicroscope, spectrophotometer and synchrotron radiation instrument. The mainachievements are listed as follows:1.(Sr,Ba)3SiO5:Eu2+was an orange phosphor which suited for blue chip excitedwarm white LED. However, it always coexisted with impurity (Sr,Ba)2SiO4:Eu2+which not only quenched the luminescence but also deteriorated the colorchromaticity of Sr3SiO5:Eu2+. In this dissertation, we put forward two methods toimprove the crystallization and luminescence properties of (Sr,Ba)3SiO5:Eu2+. Theresults indicated that the optimized ratio3:0.95of Sr/Si and10-30%nano SiO2added could promote the grain growth of (Sr,Ba)3SiO5:Eu2+. The high efficient(Sr,Ba)3SiO5:Eu2+phosphor was synthesized successfully by employing these twoachievements. In addition, we have investigated the effect of alkaline earth on theluminescence properties. Ba2+ion doped could shift the emission to about600nm,while the Ca2+ion doped decreased emission intensity and shifted the emission toshort wavelength. Morever, we proposed that the micro-scale H2O in the systemwas the accelerator of (Sr,Ba)3SiO5:Eu2+decomposition on base of the effect offlux added in the (Sr,Ba)3SiO5:Eu2+system. We mixed the modified(Sr0.8Ba0.2)2.7Eu0.3Si0.95O5with another green commercial phosphor to fabricateWLED, and detected its properties by professional test system.2. The combinational chemistry and Taguchi method was applied on thesynthesis and screening of single-phased white emitting phosphor Li2SrSiO4:Eu2+,Ce3+. On base of the emission spectra of the first combinatorial libraries, the secondscale-up samples were designed by orthogonal experiments. The effects of eachlevel on the luminescence intensity, color rendering index and color temperature were evaluated with Taguchi method. The ion Eu2+contributed most to the targetproperities, and then was the interaction of Eu2+and Ce3+, the contribution degreeof Ce3+was the least. Moreover, the two ions Eu2+and Ce3+competed with eachother on the excitation energy absorption. Therefore, the cripple of energy transferaffected the whole luminescence properties.3. In this dissertation, as for the blank application of converted fluorescentmaterial for deep ultraviolet LED chip, we proposed that the phosphor(Y,Gd)BO3:Sb3+used in PDP could be regard as the VUV(Vacuum Ultra Violet)conversion material. The luminescence properties of (Y,Gd)BO3:Sb3+on the VUVrange and corresponding electron transition among different energy levels wereinvestigated by spectrophotometer and synchrotron radiation instruments.Temperature dependence and the site-selective excitation were demonstrated atroom temperature at14K, respectively. The triplet split of excitation was attributedto the Jahn-Teller effect. Other rare earth ions co-doped in YBO3:Sb3+was alsoinvestigated, the Gd3+/Sb3+co-doped exhibited the energy transfer from Gd3+toSb3+, the Tb3+/Sb3+co-doped exhibited green emission, and the Eu3+/Sb3+co-dopedexhibited white emission, which could be used as white emitting fluorescentmaterial in deep UV excited WLED. |
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