稀土離子活化新穎螢光粉之發光特性探討及其應用

Luminescence Characterization of Rare-earth Ion Activated Novel Phosphors for LED Application

葉愷原(Kai-Yuan Yeh)

指導教授 ： 劉偉仁

中原大學/工學院/化學工程研究所/碩士(2015年)

https://doi.org/10.6840/cycu201500394

摘要

本論文主要依據螢光體設計原理，探討使用稀土離子活化新穎矽酸鹽螢光材料的合成、發光特性與機制及評估其在白色發光二極體之應用潛力。本研究利用固態反應法，於空氣或還原氣氛(氫氣/石磨)下進行燒結，成功合成摻雜稀土離子(Ce3+、Tb3+、Eu3+、Eu2+)的NaCaGaSi2O7、K2Ba5Si12O30、BaBeSiO4、NaCaBeSi2O6F等螢光材料，並利用X光粉末繞射、場發電子顯微鏡、螢光光譜與螢光生命週期進行上述材料之晶體結構、表面形貌、發光特性、色度學、熱穩定性與螢光衰退時間之鑑定。
本論文第一部份先探討三價離子(Ce3+、Tb3+、Eu3+)活化NaCaGaSi2O7主體的螢光體材料特性，考慮價數平衡採用Li+進行電荷補償，其展現Ce3+離子 f→d 躍遷寬帶特徵峰，Tb3+與Eu3+離子 f→f 躍遷特徵窄峰，且有利於UV波段上的激發；第二部份探討Eu2+離子活化K2Ba5Si12O30、BaBeSiO4、NaCaBeSi2O6F等主體的螢光材料特性，其展現Eu2+離子 f→d 躍遷的寬帶波段，因5d軌域易受晶場作用而產生分裂，本研究可觀察到離子半徑差異越大，發光中心5d軌域分裂越大，以致造成上述螢光體發光波長紅位移現象，將具有潛力的綠光K2Ba5Si12O30:Eu、藍光BaBeSiO4:Eu2+螢光體進行白色LED封裝並討論其發光特性，使用藍光BaMgAl10O17:Eu2+商品、綠光(Ba,Sr)2SiO4:Eu2+商品、紅光CaAlSiN3:Eu2+商品與搭配365 nm波長UV晶片。
上述螢光體分別放射藍光、綠光、紅光等不同色光，除可提供LED製作中螢光粉應用的新選擇之外也可避開了專利的束縛，且具有照明應用的潛力。

關鍵字

螢光粉、固態法、稀土離子、白色發光二極體

並列摘要

In this thesis, we investigated the method of synthesis, luminescencent characteristics, energy transfer mechanism and the promising application in white light emitting diodes of rare-earth ion activated novel silicate phosphors. The rare earth ion activated host with compositions of NaCaGaSi2O7、K2Ba5Si12O30、BaBeSiO4、NaCaBeSi2O6F were synthesized by solid state method under air or reducing atmosphere. The structure, surface morphology, luminescence properties, chromaticity, thermal stability and decay lifetime were characterized by X-ray diffraction, field-emission scanning electron microscope, fluorescence spectrometer and fluorescence lifetime spectrometer, respectively.
The first part examines the properties of NaCaGaSi2O7: RE (RE = Ce3+, Tb3+, Eu3+). The NaCaGaSi2O7: Ce3+ has a strong blue emission situated at 388 nm which was attributed to the f→d transition of Ce3+. The NaCaGaSi2O7: Tb3+ and NaCaGaSi2O7: Eu3+ emits green color and red color with maximum peak at 541 and 613 nm, respectively and were both attributed to the forbidden f→f transitions. NaCaGaSi2O7: RE3+ (RE: Ce, Tb, Eu) can be excited in the UV range and can be potentially applied to white-light emitting diodes；The second part investigates the luminescent properties of K2Ba5Si12O30:Eu2+, BaBeSiO4:Eu2+ and NaCaBeSi2O6F:Eu2+. The broad spectrum of these phosphors were due to f→d transition of Eu2+. The 5d orbital was found to increase with increasing the ion radii difference of the doped site as a result, the emission spectra red-shifted.
White-light emitting diodes were fabricated by using the green-emitting phosphor K2Ba5Si12O30:Eu2+ and blue-emitting phosphor BaBeSiO4:Eu2+ coupled with commercial blue-emitting phosphor BaMgAl10O17:Eu2+, green-emitting phosphor (Ba, Sr)2SiO4:Eu2+, red-emitting phosphor CaAlSiN3:Eu2+ and 365 nm chip.

並列關鍵字

phosphor ； white LED ； rare earth ion ； solid-state reaction

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