ZnS:Tb螢光體添加助熔劑發光性質之研究

A Study on Photoluminescence of ZnS:Tb phosphors added with Fluxs

陳大中(Da-Chung Chen)

指導教授 ： 唐自標

國立臺北科技大學/工程學院/材料及資源工程系所/碩士(2005年)

https://doi.org/10.6841/NTUT.2005.00167

摘要

硫化鋅具有寬能隙特性，在發光材料中，為良好的母體基材，可以利用摻雜不同的激活劑，改變其發光顏色，因此應用相當廣泛。在商業上，常被用來當作薄膜電致發光（Electroluminescence，EL）元件之一，所以有關硫化鋅的研究，很多是探討薄膜方面的發光特性，尤其是硫化鋅摻雜稀土元素，如ZnS：Tb，F，在EL上為一個很好的綠色發光體。而本研究即是利用固態反應法，製備ZnS：Tb螢光粉體。通常稀土元素離子半徑較大，較難進入ZnS晶格，取代Zn2+位置，因此也較難順利吸收能量，轉而成為稀土特有的4f軌域之間的躍遷，成為發光中心，所以ZnS單純添加Tb時，並無Tb特性光產生。不過藉由添加助熔劑，即可合成ZnS：Tb的綠色螢光體。助熔劑的添加除了幫助燒成外，也有電荷補償功能，幫助能量的傳達，對ZnS：Tb螢光體的合成相當重要，本實驗選擇六種性質相似的鹼金屬鹵素化合物，分別為LiF、LiCl、NaF、NaCl、KF、KCl六種加以探討。由實驗結果得知，當添加含有F-離子助熔劑（LiF、NaF及KF）時，其發光特性均轉為Tb3+的特性光譜，為5D4→7FJ的躍遷（5D4→7F6、5D4→7F5、5D4→7F4、5D4→7F3、5D4→7F2），光譜為線狀光譜。且通常助熔劑陽離子越大，發光強度越高，在添加Tb 0.3mole%時有最佳之發光強度。而添加含有Cl-系列助熔劑（LiCl、NaCl及KCl）時，發光光譜除了有Tb3+的特性光外，還有一寬帶的母體發光，最主要是因為Cl-跟ZnS產生自我發光中心（Self–activator）。其中，添加LiCl助熔劑時，只有母體發光，並無明顯Tb3+特性光產生。而且一樣是在Tb0.3mole %有最佳發光強度。由於助熔劑的添加，在高溫燒成下，使的燒成後晶粒的形狀、大小，有明顯的不同。含有F-的助熔劑，燒成後，不易研磨，顆粒粗大、且晶粒形狀不規則，而含有Cl-助熔劑，則有良好的晶形與顆粒大小。

關鍵字

螢光材料 ； 硫化鋅 ； Tb ； 助熔劑 ； 光致發光

並列摘要

ZnS with the characteristic of a broad energy gap is a good host material among luminescence, and it could be doped by different activators to change the light’s color, so it has been used widely. ZnS is often one part of the electroluminescene devices in commercial, so there are many researches about the characteristics of film luminescene, especially for the ZnS doped with rare-earth, such as ZnS:Tb, F, that is a good green phosphor in EL. The study of luminescence for the generation of ZnS:Tb green phosphor is using the solid state method. In general, the radius of rare-earth ions is bigger, so it is more difficult to substitute the Zn2+¬ ions in the ZnS lattice, so that 4f-4f energy transition has the difficulty that Tb can’t act as the luminescence center, so there is no characteristic spectrum of ZnS with the sole addition of Tb. But it can get the green phosphor of ZnS：Tb by added the fluxs. The addition of fluxs are not only to help firing, also have the function of charge complementation to help the transmission of energy. The fluxs are important for the mixture of the green phosphor of ZnS：Tb. This experiment select the similar properties of the alkaline halide , which are LiF, LiCl, NaF, NaCl, KF, KCl. The experiment’s result shows that when adding the fluxs with F¬¬- ions（LiF, NaF and KF）, the spectrum of ZnS transformed to the Tb3+ characteristic spectrum , that is 5D4→7FJ(5D4→7F6、5D4→7F5、5D4→7F4、5D4→7F3、5D4→7F2), and their characteristic spectrum is sharp peak. In general, when the cation ion is bigger, the intensity of luminescence is stronger. And the addition include the fluxs with Cl-（LiCl, NaCl and KCl）, the characteristic spectrum is same as the Tb3+ characteristic spectrum, and with the broad spectrum , the main reason for that is the Cl- and ZnS form the SA（Self – activator）. When the LiCl flux is added, there is only host lattice luminescence, there is no Tb3+ characteristic spectrum. The same only Tb0.3 mole % has the best luminescence intensity. By adding the fluxs with firing in high temperature, that make the shape, particle size are very different. After the fluxs including F- is fired, it’s not easy to grind , and the particle size is coarser, and the
shape is not good . By adding with Cl- fluxs has the good shape and size.

並列關鍵字

luminescence ； ZnS ； Tb ； flux ； photoluminescence

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