标题: 奈米萤光体之低温合成与光学特性研究
Synthesis and optical characterization of nanosize phosphors via low-temperature process
作者: 杨志成
Chih-Cheng Yang
陈三元
San-Yuan Chen
材料科学与工程学系
关键字: 氧化锌;铝酸锌;萤光体;奈米;气氛处理;核壳结构;低温合成;ZnO;ZnAl2O4;phosphors;nano;atmosphere annealing;core-shell structure;low-temperature systhesis
公开日期: 2005
摘要: 在本研究中,主要在探讨氧化锌、铝酸锌和卤磷酸盐的奈米萤光体化学反应合成与物性及光学性质。首先对在氧化锌生成反应,发现在ZnO/Si基板上,在60度时,可合成沿c轴方向高密度的氧化锌奈米棒。且使用氮气氛去作热处理,可以提升氧化锌奈米棒在紫外光的强度。经由EXAFS量测之后,发现到气氛可能只是被吸附或者是陷入在氧化锌奈米棒的表面。
而在奈米级铝酸锌粉体的生成,发现到pH值和反应的温度,在合成奈米尺寸铝酸锌上扮演一个很重要的角色。在pH=7,150度时,可以透过中间产物(ZnAl-LDH)的生成,进而合成平均颗粒大小在5 nm 范围的铝酸锌奈米体。当奈米体表面经过表面活性剂CTAB处理之后,则可以形成ZnAl2O4/Eu核壳结构。
进一步探讨合成奈米级的铕掺杂卤磷酸盐。发现在室温下pH=2时,可以同时生成含有Cl和OH两种不同的卤磷酸盐相。但是当pH值超过7时,只有含有OH的卤磷酸盐相会被生成。当在经过850度还原气氛热处理之后,在不同pH值下,粉体会成呈现不同的蓝色和红色放射光强度。这些结果暗示了,红光和蓝光两者之间相对的放射强度,可以藉由控制pH值(结晶相)和改变热处理的气氛来调控。
In this thesis, most of my researches were primarily focused on the synthesis and optical characterization of ZnO-based nanosized phosphors. Firstly, as the ZnO films were pre-treated with nitrogen implantation in the range from 5x10^12 to 5x10^15 ions/cm2, it was found that the peak intensity of near band-edge emission remarkably decreases with the increase of concentration of implanted nitrogen when annealed in nitrogen atmosphere. However, as the ZnO was implanted with 5x10^12 ions/cm2 and annealed in oxygen atmosphere, the optical properties are improved probably.
Subsequently, high-density ZnO nanorods can be vertically grown on Si coated with ZnO film (ZnO/Si substrate) from aqueous solution at 60oC. It was observed that enhancement of PL properties due to N2-atmosphere annealing for ultraviolet emission was obtained and can be attributed to the reduction of defect density. The extended x-ray absorption fine structure (EXAFS) reveals that most ions are possibly trapped or adsorbed on the surface of the ZnO nanorods and thus, the annealing atmosphere shows no apparent influence on the deep-level defects of ZnO nanorods.
In addition, europium doped nanocrystalline zinc aluminate (ZnAl2O4) particles were prepared by hydrolyzing a mixture of aluminum chloride hexahydrate and zinc chloride in deionized water. At pH=7 and T>120oC, the nanocrystalline ZnAl2O4 particles with average particle size of ~5 nm are easily synthesized through ZnAl layered double hydroxide (ZnAl-LDH). After surface treatment with the cationic surfactant CTAB, the ZnAl2O4/Eu core-shell structure may be developed. The ZnAl2O4/Eu core-shell structure can show both emissions from 5D0 to 7F2 sensitivity energy level and 5D2 to 7F0 depth energy level.
Finally, the synthesis and optical properties of nanocrystalline Eu-doped halo-phosphate powders, Ca5(PO4)3(OH):Eu3+, were also investigated. At pH=2, both Ca8.3Sr1.7(PO4)6Cl2 and Ca8.3Sr1.7(PO4)6B(OH)2 phases were detected, but for the solution with pH value over 7, only one Ca8.3Sr1.7(PO4)6(OH)2 phase was identified. After annealed at 850oC in a reduction atmosphere, different relative ratio of blue and red emissions can be controlled through changing the various pH-solutions. These results indicate that the relative peak intensity of both red and blue emissions can be tunable by controlling the solution pH value (crystalline phase) and changing annealing atmosphere.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT008918807
http://hdl.handle.net/11536/77835
显示于类别:Thesis


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