新穎稀土摻雜氟硫化物與硫氧氟化物螢光材料之製備與發光特性研究

Abstract

為持續發掘新穎化學組成之白光發光二極體螢光粉，本研究利用高溫固態反應於密閉石英玻璃管中，於850-1000℃與1150℃分別成功製備Ce3+與Eu2+激活之單一系列Y3S2OF3:Ce3+氟氧硫化物螢光體與四系列La2MF4S2: Ce3+ (M = Ca, Sr)與La2MF4S2:Eu2+ (M = Ca, Sr)氟硫化物螢光體。X光繞射儀、螢光光譜儀、電子顯微鏡被用以進行合成條件最適化與活化劑摻雜濃度測定、晶相鑑定、晶體結構精算、漫反射光譜、發光與激發光譜、溫度依存熱消光光譜測定、色座標值與量子效率以及螢光體微結構分析鑑定。 Y3S2OF3:Ce3+與La2MF4S2: Ce3+ (M = Ca, Sr)之激發與放射分別源自於Ce3+中電子4f 1→5d 1的吸收與5d 1→4f 1放寬帶射躍遷；而La2MF4S2:Eu2+ (M = Ca, Sr)之激發與放射則分別源自於Eu2+中電子4f7 → 4f 65d 1的吸收與4f 65d 1→4f 7放寬帶射躍遷。Ce3+或Eu2+摻雜之新穎氟硫化物與硫氧氟化物螢光粉，激發波長由250 nm至藍光425 nm，而放射波長則由藍光425 nm至紅光750 nm以上，幾乎涵蓋了整個可見光範圍。其中La2CaF4S2:Eu2+與La2SrF4S2:Eu2+皆能放射波長涵蓋600至800 nm的罕見深紅至紅外光，尤為特別。 本研究中所合成五系列螢光體具有較傳統硫化物螢光體更佳之熱消光特性，具有可提供製作白光LED之潛力。

Fluorosulfide and oxyfluorosulfide-based phosphors have relatively low synthetic temperature and appropriate excitation wavelengths for applications in fabricating white-light LEDs. To enhance the thermal stability of sulfides, we choose the fluorosulfides and oxyfluorosulfide as host matrices and activated with Ce3+ and Eu2+ as activator, respectively. In this study, we have prepared five series of fluorosulfide and oxyfluorosulfide phosphors, viz., Y3S2OF3:Ce3+, La2MF4S2:Ce3+ and La2MF4S2:Eu2+(M = Ca, Sr) using sealed quartz tube at 850-1000℃and 1150℃, respectively. These phosphors can be excited by radiation with wavelength ranging from 300 nm to 500 nm and their emission colors almost cover the whole visible spectral range. The content of this thesis can be divided into two parts. Firstly, we will introduce the background knowledge of phosphors used in LEDs, and then elaborate the design rules, the motivations and goals of the study. The synthetic methods and further characterization results will be discussed in the second part.