以溶膠-凝膠法製備LaAlO3: Ce粉末結構與光學特性之研究

發光材料大部分是藉由內部原子占據主體晶格之位置或電子躍遷導致能量放射進而產生光，故螢光粉於材料的選擇上非常重要，而鋁酸鑭(LaAlO3)為一較新穎之材料，其具有良好的化學穩定性、機械耐久性及光學活性等特性，在近幾年來成為了發光材料研究重點之一，而Ce離子其電子組態之緣故，在接收激發能量後可遵守選擇率做f→d能階之允許躍遷，因此Ce除了工業上用途外，於發光材料的應用上也頗具研究價值。本實驗製備樣品粉末之方法為溶膠-凝膠法，以三嵌段兩性共聚物F-127做為有機分子模板，再分別以硝酸鋁、硝酸鑭及硝酸鈰做為LaAlO3及摻雜元素Ce離子之前驅物，藉由摻雜不同比例之Ce及不同製程溫度煆燒後獲得LaAlO3: Ce樣品粉末，最後經由X-Ray繞射分析(XRD)、掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)等材料分析及紫外-可見光譜(UV-Vis)和螢光光譜分析(PL)等光學特性分析來探討其結構及性質。由XRD分析結果得知利用溶膠-凝膠法於900 ℃以上即可合成出LaAlO3之粉末，其晶粒大小約為30.24 nm，屬於三方晶系中之菱面體，且摻雜濃度提升至0.02 mol%以上時，晶粒尺寸有被抑制而縮小的趨勢。由UV-Vis分析結果可看出摻雜之樣本於波長312 nm處有最強烈的吸收峰，此為Ce3+離子的4f-5d躍遷之吸收峰，且吸收強度隨著摻雜濃度提高而上升，而各樣本以247 nm之波長做激發可發散出藍光，以312 nm波長做激發可得接近白光之藍綠光。

關鍵字

鋁酸鑭；溶膠-凝膠法；鈰摻雜；光致發光

並列摘要

Lanthanum aluminates(LaAlO3) an interesting luminescent materials. The material, which has good chemical stability, mechanical durability and optical activity, those are the reasons why LaAlO3 become the emphasis of researches recently years. Due to the electronic configuration of Ce ion, so it can receive excitation energy to achieve transition of 4f-5d energy level. Therefore, it’s available research increasing important in the application of luminescent materials. In this experiment, we prepared LaAlO3: Ce by sol-gel method, and using triblock copolymer F-127 as organic template, aluminum nitrate, lanthanum nitrate and cerium nitrate as precursors. By doping different concentrations of Ce and different temperatures to obtain LaAlO3: Ce samples. Finally, the structure and optical properties are investigated by X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis spectroscopy and fluorescence spectroscopy (PL). XRD analysis shows the powder of LaAlO3 can be synthesized by the sol-gel method at 900 °C calcination. The grain size is 30.24 nm, which is rhombohedra of the trigonal system. The grain growth will inhibit when the doped concentration exceed 0.02 mol%. According to UV-Vis analysis, it can observe that has strong absorption at 312 nm, the absorption phenomenon is occurring by Ce3+ electronic transition, and the absorption intensity increases with the doping concentration. Each samples can emit blue light which are excited by 247 nm, the greenish-blue light close to white light can excited by 312 nm.