稀土摻雜鹼土鎵硫化物與鎵硫氧化物螢光體之合成與發光特性鑑定

Abstract

本研究利用固態法製備SrLaGa3S6O：Ln (Ln= Ce3+、Eu2+)、CaLaGa3S6O：Eu2+與Sr2Ga2S5：Ce3+三系列螢光體，並以紫外-可見光全反射光譜、X-ray粉末繞射、螢光光譜、量子效率與色度座標分析對上述螢光體之結構、發光特性及色度學特性進行分析鑑定，其主旨在於開發新穎且具有應用價值之螢光體。 本論文第一部份探討不同主體之最佳合成條件與X光繞射晶相之分析鑑定；第二部份探討Ce3+摻雜不同主體之發光特性，並針對摻雜離子取代格位環境與發光波長的關聯性做進一步之探討；第三部分則探討SrLaGa3S6O：Ce3+, Eu2+中Ce3+與Eu2+間的能量轉移機制；第四部分探討CaLaGa3S6O：Eu2+的發光特性，第五部分探討上述三系列螢光體之熱消光效應，以作為白光發光二極體應用之參考。

In an attempt to investigate phosphors for light emitting diode (LED) application, we have successfully synthesized four series of thiogallate and oxythiogallate phosphors with compositions of SrLaGa3S6O:Ln (Ln = Ce3+, Eu2+, Ce3+/Li+ or Ce3+/Eu2+), (Sr1-xAx)LaGa3S6O:Ce3+ (A = Ca, Ba), Ca(La1-yMy)Ga3S6O:Ce3+ (or Eu2+) with M = Y, Gd,, and Sr2Ga2S5:Ce3+, respectively, by solid-state method under reduction atmosphere of H2S/Ar. .The crystal structure, luminescence, chromaticity and thermal luminescence quenching properties have been characterized by using X-ray diffraction (XRD), diffuse reflectance, and fluorescence spectroscopy. We first investigated the optimization of synthetic conditions of all phosphors and carried out phase identification using XRD. We then investigated luminescence spectra of thiogallate and oxythiogallate and found that both can be excited in the range of 300-450 nm with optimal excitation at 397 nm (Ce3+-activated phases) and 405 nm (Eu2+-activated phases), respectively. The effect of crystal field strength on the luminescence of the (Sr1-xAx)LaGa3S6O:Ce3+ (A = Ca, Ba) and Ca(La1-yMy)Ga3S6O:Ce3+ (M = Y, Gd) systems has also been studied by cation substitution for Sr2+ and La3+, respectively. The energy transfer from Ce3+ to Eu2+ in SrLaGa3S6O:Ce3+,Eu2+ was investigated and found to occur via a resonance-type dipole-dipole mechanism. The chromaticity coordinates of SrLaGa3S6O:5%Ce3+,xEu2+was observed to shift from blue to yellowish-green with x increasing from to 0.10. Furthermore, the charge compensation study revealed that the emission spectrum of charge-compensated SrLaGa3S6O:Ce3+,Li+ red-shifted as compared to that of the uncompensated (Sr1-nCen)LaGa3S6O phase. Finally, we have studied the temperature-dependent luminescence intensity for the SrLaGa3S6O:Ln (Ln = Ce3+, Eu2+) and Sr2Ga2S5:Ce3+ phosphors and discovered that the thermal quenching was observed to be more serious in Sr2Ga2S5:Ce3+ than that observed in SrLaGa3S6O:Ln.