奈米鋁酸鍶與硫化鋅螢光材料製備及光學與結構之特性研究

Luminescent and Structural Analysis of Nanosized Strontium Aluminate and Zinc Sulfide Phosphors

陳師彥(Shih-Yen Chen)

指導教授 ： 呂宗昕

國立臺灣大學/工學院/化學工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.00509

摘要

本論文的第一部份成功地以新穎的逆微乳膠法合成出摻雜銪、镝離子的鋁酸鍶螢光體。採用本製程，最大的特色在於奈米尺度的微胞反應器的生成時，可以有效的減少原子與原子間反應時的擴散距離，進而增加前驅物的反應性，來降低合成溫度。在本實驗中，不但有效地將鋁酸鍶的合成溫度降低到900度左右，同時也將螢光粉體粉體的粒徑縮小至奈米尺度。在螢光特性上，可以清楚的觀察到隨著粉體結晶性的提升，螢光強度有明顯增加的趨勢外，同時也可以發現當螢光體降低到奈米尺度的範圍時，激發與放射峰的位置會產生藍移的現象。而在餘暉方面，也可以觀察到隨著煅燒的溫度提升，餘暉衰減速度有明顯下降的趨勢。

本論文的第二部分在研究以異己酸鋅當作鋅的前驅物，並採用微波法來進行合成奈米級硫化鋅摻雜錳離子螢光體。在本製程當中，不但可以有效的在硫化鋅表面形成異己酸根的鍵結，並藉由此鍵結鈍化表面的缺陷，進而提高螢光強度。本實驗使用FTIR及XPS等測量儀器，來證明表面鍵結的型態是由在同一個酸根中的兩個對稱氧原子同時鍵結再同一個鋅原子上。上述所提的陰離子團，除了表面鈍化作用外，同時也使得螢光體表面帶有相同電性的電荷，藉由此電荷的排斥效應可以改善奈米粉體的聚集現象。並藉由ESR的顯微結構結果發現，在本次實驗當中硫化鋅晶格中所摻雜的錳離子彼此間具有良好的分散性。螢光特性上，本次製備的奈米級硫化鋅摻雜錳離子螢光體，在585 nm左右(4T1->6A1的電子躍遷)，產生一個非常明亮的黃橘色放射峰，再次證明所摻雜的錳離子有效的進入晶格當中並取代鋅原子的位置。

本論文的第三個部份，在探討上述實驗中，微波能量的改變對於奈米級硫化鋅摻雜錳離子螢光體的物理特性影響。由實驗結果可以發現，經由不同的微波能量下所合成的螢光體，其粉體尺寸有著些許的差異性，而由於量子效應的關係，造成硫化鋅的能隙跟著程度上的變化，並進一步反應在放光的位置上。同時也可以清楚的發現，在微波能量為300W的條件下，具有最強的放射能力，經由ICP的量測後，可以發現是由於錳離子進入晶格的數量最多的原因所造成。藉由本實驗的結果，可以得知在微波能量為300W的條件下，本製成具有最適合的反應環境。

關鍵字

奈米 ； 鋁酸鍶 ； 硫化鋅 ； 螢光材料

並列摘要

In the first part of this thesis, synthesis of Eu2+, Dy3+ -activated strontium aluminate nanosized phosphors via a novel reverse microemulsion process is reported. This new synthesis technique not only reduced the synthesis temperature of SrAl2O4:Eu2+, Dy3+ phosphors to as low as 900oC, but also reduced the phosphor particle size to nanometer scale. In the microemulsion process, nanometered-micellees trapped the constituent cations, leading to a reduction of the interdiffusion length and an enhancement of the reactivity of the precursors. The photoluminescence intensity of prepared phosphors was found to substantially depend on their crystallinity and the results also indicated that the main peaks of nanosized SrAl2O4:Eu2+, Dy3+ phosphors in the excitation and emission spectrum shifted to shorter wavelengths. The decay time of prepared phosphors was greatly increased when synthesized at elevated temperature.

In the second part of this thesis, synthesis of highly luminescent ZnS: Mn2+ nano-particles via a microwave irradiation technique using zinc 2-ethylhexanoate as a novel zinc precursor is reported. This process was revealed as an efficient technique for producing in-situ capping of 2-ethylhexanoic acid on the ZnS: Mn2+ nano-particle surface, resulting in high luminescence intensity due to effective surface passivation. The chemical interaction of the carboxylic acid group with the ZnS: Mn2+ nano-particle was investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The obtained results indicated that 2-ethylhexanoic acid is chemisorbed as a carboxylate onto the surface of ZnS:
Mn2+ nano-particles and the two oxygen atoms in the carboxylate are coordinated symmetrically to the Zn atoms, leading to the formation of the covalent Zn-O bond. The anion bound onto the nano-particle surface prevents particle agglomeration due to electrostatic repulsion between two adjacent particles. Electron spin resonance (ESR) study showed a hyperfine sextet indicating well separated Mn2+ states without agglomeration. The prepared ZnS: Mn2+ nano-particles showed bright yellow-orange luminescence at about 585 nm, characteristic of 4T1 (excited)-> 6A1 (ground) transition of Mn2+ ion at Td symmetry in ZnS crystals.

In the last part of this thesis, the effect of microwave irradiation power on the physical properties of ZnS: Mn2+ nanophosphors is investigated. A series of ZnS: Mn2+ nanoparticles is synthesized changing the microwave power (from 150 W-500 W) to study its effect on the physical properties of the ZnS:Mn2+ nanoparticles, when all other synthesis conditions are kept fixed. From the obtained experimental results, it is observed that with changing power, there is also some effect in the particle size, leading to change the band gap of the prepared nano-phosphors. In the photoluminescence spectra, the blue shift phenomena is also revealed due to the quantum size effect and the sample synthesized with microwave power of 300 W showed highest luminescence intensity because of more manganese ions going inside the host lattice. From this experiment, the synthesis condition with microwave power at 300W is proven to be the optimum condition for synthesizing the nano ZnS: Mn2+ phosphors in this process.

並列關鍵字

nano-phosphors ； strontiu ； aluminate ； zinc sulfide

參考文獻

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