本研究利用固態反應法合成近紫外光激發之矽酸鹽類BaZr1-yHfySi3O9:Eu2+藍綠色螢光粉與Li2SrSi1-yTiyO4:Eu2+黃色螢光粉，利用兩種螢光粉搭配近紫外光發光二極體(Light-emitting Diodes, LEDs)混合成白光，然而近紫外光LED操作時表面溫度會變高，故螢光粉需要更好的熱穩定性，且近紫外光激發螢光粉發光強度不高，因此本研究著重於改善螢光粉之熱穩定性及發光強度。前者藍綠色螢光粉隨Hf4+摻雜濃度提升熱穩定性(T50由230 °C提高到281 °C)；後者黃色螢光粉摻雜Ti4+發光強度提升14.15%，兩者皆具較寬之激發光譜，皆適用於近紫外光LED。
其中BaZr1-yHfySi3O9:Eu2+藍綠色螢光粉利用Hf4+取代Zr4+，Hf之質量較大，因此晶格振動受熱影響變小，活化能變大(由0.374 eV提升至0.3832 eV)，降低非輻射緩解的機率，但由於摻雜Hf4+時會有雜相產生，隨Hf4+濃度變大，發光強度大幅降低；最後選擇加入NH4Cl作為助熔劑，可幫助結晶反應，使結晶性更好，減少雜相，以6 wt% NH4Cl為最佳濃度，其發光強度大幅提升，且維持較佳熱穩定性。Li2SrSi1-yTiyO4:Eu2+黃色螢光粉則利用Ti4+取代Si4+，Ti4+使平均晶粒大小變大(從65.71 nm至70.47 nm)，最佳摻雜濃度為0.02 mol%，而發光強度會隨Crystallite size變化。
將上述之BaZr1-yHfySi3O9:Eu2+藍綠色螢光粉及商用(Ba, Sr, Ca)2SiO4:Eu2+黃色螢光粉，搭配近紫外光(395-400 nm) LED產生白光。本研究採取與以往不同的螢光膠薄層結合反射杯製備可置換式白光LED，其優點為可任意拆裝，調變不同參數於單一LED，可任意調整白光LED之特性，藉由不同片數以找出最佳白光LED的特性，本研究最佳化元件特性:白光CIE座標為(0.325,0.358)，照明效率為20.9158 lm/W，演色性為80.47。

In this study, BaZr1-yHfySi3O9: Eu2+ and Li2SrSi1-yTiyO4: Eu2+ silicate phosphors were synthesized by the solid-state reaction method, which could be well excited by near-ultraviolet (UV) light. Using near-UV light-emitting diode (LED) chip to excite cyan and yellow color phosphors was a feasible way to generate white light. However, due to higher operating temperature for UV-LEDs, phosphors with better thermal stability became crucial. Thus, this work focused on improving the thermal stability and the luminous intensity. The thermal stability of the former was improved with increasing the concentration of Hf4+ ions. T50 value (the temperature at which the emission intensity falls to 50% of that at room temperature) was enhanced from 230 to 281 °C. Besides, the emission intensity of the latter was enhanced 14.15% by doping Ti4+. Because of their broad excitation spectra, these phosphors could be applied on the near-UV LEDs to form the phosphor-converted white LEDs (pc-WLEDs).
The thermal stability of BaZr1-yHfySi3O9:Eu2+ phosphors enhanced due to the substitution of Zr4+ by Hf4+ ions, which affected smaller lattice vibrations by phonons from heating. Therefore, the activation energy was increased from 0.374 to 0.3832 eV, reducing the probabilities of non-radiative reaction. However, due to the doping of Hf4+, the emission intensity decreased apparently with the increasing concentration of Hf4+ with impurity phase.Finally, NH4Cl was added to raw material as flux and promoted the crystallization reaction. The optimal concentration of NH4Cl was found to be 6 wt%. Besides, Li2SrSi1-yTiyO4: Eu2+phosphors were doped by Ti4+, which leads to larger crystallite size, from 65.71 to 70.47 nm. The optimal concentration of Ti4+ was 2 mol% and the emission intensity could depend on the crystallite size.
For the WLED application, BaZr1-yHfySi3O9:Eu2+ cyan phosphors and commercial (Ba, Sr, Ca)2SiO4:Eu2+ yellow phosphors were combined with near-UV-LEDs (λex=395-400 nm) to generate white light. In the past, the conventional dispensing technology was directly coating on chip. In this study, the reflector cup was combined with phosphor films to form replaceable white LEDs. It takes significant advantages for practical applications such as detachable, low-cost, and one LED with various parameters for characteristics of white LED. By modulating number of different pieces of phosphor films, it is suitable to find the optimal characteristics of the white LEDs. The optimum luminous efficiency, CIE coordinates, and CRI of the final proposed devices were 20.9158 lm/W, (0.325, 0.358), and 80.47, respectively.

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