螢光粉是一種非常普及的發光材料，常用於LED、霓虹燈、防偽標籤等等領域。矽酸鋁二鈣 (Gehlenite) 是一種螢光粉母體材料，擁有良好的化學及熱穩定性，因此具有相當重要的應用性質。三價銪 (Eu3+) 是一種常見的紅光激發因子，因為與矽酸鋁二鈣有較高的發光匹配度，因而採用銪作為激發因子。螢光粉分為兩類，一類是結晶性螢光粉，另一種為非晶性螢光粉，在之前的文獻中，大部分在探討結晶性螢光粉的性質與應用，只有極少數的文獻是討論非晶性螢光粉，因此本實驗將探討以矽酸鋁二鈣作為基底，而銪作為激發因子的非晶性螢光粉。本研究發現非晶性螢光粉與結晶性螢光粉的性質大相逕庭，非晶性螢光在多孔結構中，其發光效率較高；結晶性螢光粉在多孔結構中，其發光效率較低。又因非晶性螢光粉相較於結晶性螢光粉較難以被定量分析，而可作為良好的防偽標籤，因此非晶性螢光粉是非常具有學術價值的研究。

本研究主要使用噴霧熱解法 (Spray Pyrolysis, SP) 來製備矽酸鋁二鈣摻雜Eu (Gehlenite) 螢光粉材料，使用X光繞射儀進行結晶性分析，再以掃描式電子顯微鏡觀察其表面形貌，並利用穿透式電子顯微鏡確定其結構，最後使用光致發光光譜儀（photoluminescence）得到其發光性質。本實驗細分為四個實驗，第一個實驗為調配前驅物溶液濃度，發現其濃度越高，製備粉末粒徑越大顆，發光效率越高。第二個實驗為改變矽源的前驅物，使用兩種不同醋酸矽及矽酸乙酯作為矽的前驅物，發現以醋酸矽作為前驅物時，可以得到比以矽酸乙酯作為前驅物時較多的多孔結構顆粒，而其發光效率較高。第三個實驗為利用不同造孔劑 (聚乙二醇 (PEG)、雙氧水 (H2O2)) 製備各種結構非晶螢光粉，可得到實心、多孔及中空結構的非晶螢光粉，其中利用H2O2作為造孔劑製備的中空結構非晶螢光粉的發光效率最高，可以看出螢光強度為中空粉末>多孔粉末>實心粉末的趨勢。最後一個實驗為製備好的螢光粉使用不同氣氛下進行退火空氣 (氧分壓2.1 × 10-1 atm) 、氮氣 (氧分壓1 × 10-5 atm) 及氮氫混合氣 (氧分壓1 × 10-20 atm) ，發現在低氧分壓的氮氫混和氣體中退火之螢光粉在光致發光光譜儀分析中，其主波峰有往紅光方向偏移、綠光波長變強的變化。透過SP法成功控制多種形貌粉體以及峰值變化，至於形貌對於螢光粉發光效率的影響，實心非晶結構螢光粉材料由於顆粒間能量傳輸與非輻射途徑散失產生螢光淬滅現象，因此大大影響其螢光性質；螢光峰值變化可能原因是氫氣將Eu3+還原成Eu2+，價數的改變使能帶變寬，放出的能量變大而使波峰變化。

Phosphor is a very popular luminescent material used in LED, neon, security labels and so on. Gehlenite is a phosphor host material that has good chemical and thermal stability properties and therefore it has a very wide application. Europium (Eu3+) is a common red-light excitation factor that uses europium as an excitation factor because it has a higher luminescence match with gehlenite. Phosphors are divided into two types, one is crystalline phosphors, the other is amorphous phosphors. In the previous studies, most of those are focused on crystalline phosphors, and only very few studies discuss about amorphous phosphors, so this experiment will focus on amorphous phosphors with europium as an excitation factor and using gehlenite as a substrate. The study found that amorphous phosphor and crystalline phosphor have very different properties, amorphous phosphor in the porous structure has higher luminous efficiency; crystalline phosphor in the porous structure has lower luminous efficiency. Compared with crystalline phosphors, amorphous phosphors is more difficult to be quantitatively analyzed, so amorphous phosphors can be used as security labels. Therefore, amorphous phosphors have a great value in academic research.

In this study, amorphous gehlenite：Eu phosphorous powders were synthesized by spray pyrolysis (SP). The amorphous structures of gehlenite：Eu particles were characterized by X-ray diffraction. The morphologies of the gehlenite：Eu were observed by scanning electron microscopy, and then use transmission electron microscopy to determine its structure. The final step is using photoluminescence (PL) spectroscopy to analyze its luminous properties. The experiment can be subdivided into four experiments. The first experiment was to adjust the concentration of precursor solution. The higher the concentration, the particle size becomes bigger, then the higher the luminous efficiency. The second experiment was to change the silicon precursors using silicon acetate and tetraethoxysilane (TEOS) as the silicon precursor. We found that more porous structure particles were synthesized when silicon acetate was used as a silicon precursor than TEOS as a silicon precursor which also has higher luminous efficiency. The third experiment was using different pore-forming agent, namely poly (ethylene oxide) (PEG) and hydrogen peroxide (H2O2) to synthesize a variety of structural amorphous phosphor which can be solid, porous and hollow structure of amorphous phosphor. As the result, we found that hollow structure synthesized by H2O2 as the pore-forming agent has the highest luminous efficiency in the various structural amorphous phosphor powders. We can found that the trend of photoluminescence properties is hollow particles, porous particles and solid particles (from highest to lowest). In the last experiment, the phosphors were annealed under different atmospheres, namely air (partial pressure of oxygen is 2.1 × 10-1 atm), nitrogen (partial pressure of oxygen is 1 × 10-5 atm) and the mixed air of 95% nitrogen and 5% hydrogen (partial pressure of oxygen is 1 × 10-20 atm). It was found that the phosphors annealed in 95% nitrogen and 5% hydrogen (low partial oxygen pressure) showed the main peak shift to the higher wavelength (red light) and the green light becomes stronger in the photoluminescence spectrometer analysis. We successfully controlled multiple particle morphologies and peak shift. As for the effect of morphology on phosphors luminous efficiency, the amorphous solid phosphors have fluoresce quenching due to the energy transfer and loss in non-violation way, affects the luminous property greatly. The PL peak shift may due to the hydrogen reduce Eu3+ to divalent europium (Eu2+). The change of valence number can make the band gap wider, the more energy release and the peak shifts.

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