Tb3+共摻雜與硼矽玻璃對於微波輔助燒結合成Sr2SiO4:Eu3+之發光特性及顯微結構之影響

Study of phosphor in glass of Sr2SiO4 doped with Eu3+ and co-doped with Tb3+

許嘉哲(Chia-Che Hsu)

指導教授 ： 施永輝

共同指導教授 ： 楊茹媛(Ru-Yuan Yang)

義守大學/理工學院/材料科學與工程學系/碩士(2016年)

摘要

1996 年日亞化學Nakamura 等人成功開發出藍光發光二極體，隨後搭配黃色螢光粉即摻鈰之釔鋁石榴石(cerium doped yttrium aluminum garnet,YAG:Ce)，成功開發出白光LED。然而，藍光LED晶片搭配YAG 雖發光效率佳，但有藍光轉換效率不佳以及其白光演色性不高之問題。故探索熱穩定性佳和高功率之矽酸鍶螢光粉為本研究之重要目的。
本研究延續實驗室楊育愷學長以微波燒結製備Sr2SiO4：Eu3+螢光粉 ，主要目的為開發新型矽酸鹽螢光材料並研究其特性，在主體方面採用Orthorhombic結構之矽酸鍶(Sr2SiO4：Eu3+)為基礎，分別添加金屬離子Eu3+當作活化劑發光中心及高純度玻璃粉及低純度玻璃粉為助熔劑，並分別探討摻雜濃度及燒結溫度對矽酸鍶(Sr2SiO4：Eu3+)之微結構與光學性質之研究。主要的分析係使用掃描式電子顯微鏡(Scanning Electron Microscope, SEM)、X-光粉末繞射儀(X-ray Diffraction, XRD)、光致發光光譜儀(Photoluminescence Spectrum, PL)。其中活化劑Eu 用來取代主體晶格中Sr 的位置，其參數為(熱處理條件、活化劑濃度、助熔劑添加量、持溫時間) ，探討其微結構與光學特性。
1. 以微波燒結製備之Sr2SiO4：Eu3+螢光粉，於低溫燒結條件下(900 ℃ ) ，即可形成α- Sr2SiO4 正交晶體 (Orthorhombic)，此外，隨著燒結溫度的提升發光強度亦隨之增加。根據本實驗室楊育愷學長之研究發現當Sr2-xSiO4: xEu3+ 中x=0.1 時溫度燒結條件(1200 ℃ )時其發光強度最大，推測此時活化劑濃度達最適濃度。另外，根據文獻報導與實驗室過去之研究，添加助熔劑玻璃粉亦能夠提升螢光粉的發光強度，提升結晶性，降低燒結溫度等優點並可利用Tb3+共摻雜調整發光波段，且隨著玻璃粉純度的不同及添加量的增加發光強度亦隨之提升。
2. 由分析結果顯示， 以上述發光強度最強之螢光粉，即添加於Sr2SiO4：Eu3+內，加入助熔劑：低純度玻璃粉，由分析結果可得知其最佳之摻雜濃度為0.10wt%、燒結溫度維持1200℃。由XRD分析中，可得知當摻雜量由0.05wt%增加至0.25wt%所製備之Sr2SiO4：Eu3+：低純度玻璃粉皆為純相。並可知道當摻雜度超過上述之最佳值時，會導致在Sr2SiO4：Eu3+低純度玻璃粉有晶粒團聚現象，進而影響其發光強度，可推測為是因其摻雜濃度已超過飽和濃度而造成濃度淬滅，而導致其發光強度衰減。
3. 再以上述發光強度最強之螢光粉，即添加於Sr2SiO4：Eu3+內，加入助熔劑：高純度玻璃粉，由分析結果可得知其最佳之摻雜濃度為0.10wt%、燒結溫度維持1200℃。由XRD分析中，可得知當摻雜量由0.05wt%增加至0.25wt%所製備之Sr2SiO4：Eu3+高純度玻璃粉皆為純相。並可知道當摻雜度超過上述之最佳值時，會導致在Sr2SiO4：Eu3+高純度玻璃粉有晶粒團聚現象，進而影響其發光強度，可推測為是因其摻雜濃度已超過飽和濃度而造成濃度淬滅，而導致其發光強度衰減。
4. 最後，經實驗結果發現添加助熔劑：高純度玻璃粉及低純度玻璃粉之Sr2SiO4：Eu3+ 螢光粉，發光強度並無巨大差異，故以低純度玻璃粉為助熔劑進行降低燒結溫度實驗，此舉為降低螢光粉製作成本為出發點而設計，由實驗發現將燒結溫度降至1100℃時，由XRD分析中，可得知當摻雜量由0.05wt%增加至0.25wt%所製備之Sr2SiO4：Eu3+低純度玻璃粉已有雜相產生。
5. 摻雜活化劑Tb3+：當燒結溫度為1200℃，Sr2SiO4：Eu3+ 為純相，摻雜濃度之最佳值為0.30wt%，可得知當摻雜量由0.025wt%增加至0.35wt%當激發波段於237nm，可得最強之放射波段550nm屬於5D4-7F5之電子躍遷。CIE色度座標隨著添加物Tb3+摻雜濃度增加而改變，由紫光慢慢偏向介於紅光與綠光之間。

關鍵字

螢光粉 ； 光致發光 ； 發光二極體 ； 微波燒結法

並列摘要

In 1996, the white LEDs were fabricated with blue LED chips and yellow phosphors such as cerium doped yttrium aluminum garnet (YAG:Ce) by Nichia. Although the blue chip based white LEDs have high brightness and efficiency, they still have some problems such as low color rendor index and low reproducibility. The objects in this thesis are to find a phosphor with high thermal stability and high power density.
This study continues the Yu-kai Yang lab senior in microwave sintering of Sr2SiO4:Eu3+ phosphor, The main purpose of developing a new type of fluorescent material of silicate and study their characteristics. In the aspect of subject by Orthorhombic structure of the silicon strontium Sr2SiO4:Eu3+ based, respectively, with the addition of metal ions (Eu3+) as activating agent luminescence center and high purity glass powder and low purity glass powder as a flux in the, and doping concentration and sintering temperature on silicic acid strontium (Sr2SiO4:Eu3+) micro structure and optical properties of research are discussed. The main analysis using scanning electron microscopy (scanning electron microscope, SEM), X-ray powder diffraction X-ray diffraction (XRD), light induced luminescence spectrometer (increasing spectrum and PL). The activation agent EU used to replace the position of the host lattice in Sr, the parameters (thermal processing conditions, activation agent concentration), adding amount of flux, temperature and time) on the microstructure and optical properties.
1. Prepared by microwave sintering of the Sr2SiO4:Eu3+ fluorescent powder, in under the condition of low temperature sintering (900 ℃) can be formed alpha Sr2SiO4 orthogonal crystal Orthorhombic. In addition, with sintering temperature ascension luminous intensity is also increased. According to the found of the laboratory fellow students Yang Yukai when Sr2-xSiO4: xEu3+=0.1 sintering temperature conditions (1200℃) the maximum luminous intensity, suggesting that this activation agent concentration was reached the optimal concentration degree. Also according to the reported in the literature and laboratory in the past research, add flux of glass powder can enhance the luminescent intensity of the phosphors, enhance the crystallization, the lower the sintering temperature and other advantages and using Tb3+ Co-doped adjust the luminous band, and with glass powder purity of different and Tim plus the amount of increase in the PL intensity also increased
2. By the analysis results show that the luminescence intensity is the strongest of phosphors, is added in the Sr2SiO4:Eu3+, adding flux: low purity of glass powder. By analysis result can be that the optimal doping concentration maintains a 1200℃for 0.10wt%, sintering temperature. By the XRD analysis, it is found that when the doping amount is increased from 0.05wt% to 0.25wt%: low purity glass powder is pure phase. And know when the doping degree more than the optimum value, resulting in Sr2SiO4:Eu3+ low purity of glass powder is the aggregation of grains, thereby affecting the luminous intensity, presumably is due to the doping concentration has exceeded the saturation concentration caused by concentration quenching, which led to the luminescence intensity attenuation.
3. Then the luminescence intensity is the strongest of phosphors, is added in the Sr2SiO4:Eu3+, adding flux: high purity glass powder, by the analysis results can be learned that the optimal doping concentration maintains a 1200 ℃ for 0.10wt%, sintering temperature. By XRD analysis, it is found that when the doping amount is increased from 0.05wt% to 0.25wt% high purity glass powder is pure phase. And know when the doping degree more than the optimum value, resulting in Sr2SiO4:Eu3+ high purity glass powder is the aggregation of grains, thereby affecting the luminous intensity, presumably is due to the doping concentration has exceeded the saturation concentration caused by concentration quenching, which led to the luminescence intensity attenuation.
4. Finally, the experimental results, it is found that adding flux: high purity glass powder and low purity of glass powder Sr2SiO4:Eu3+ phosphor, luminescence intensity had no great difference, so to low purity of glass powder as fluxing agent to reduce the sintering temperature experiment, the move to reduce fluorescent powder made into this as a starting point and design, by experiment, it is found that the sintering temperature is reduced to 1100 ℃, by XRD analysis, that when doping amount by 0.05wt% increase to 0.25wt% of prepared Sr2SiO4:Eu3+ low purity glass powder has been mixed phase.
5. Doping activator Tb3+: when the sintering temperature is 1200℃, Sr2SiO4:Eu3+ for pure phase, the doping concentration of the best value for 0.30wt%, we can see that when the doping amount by 0.025wt% increased to 0.35 when the excitation band in 237nm, the strongest radiation at 550nm band belongs to the electronic transition of the 5D4-7F5. CIE chromaticity coordinates with additives increasing the Tb3+ doping concentration changed slowly by the purple bias between red and green.

並列關鍵字

phosphor ； photoluminescence ； LED ； microwave sintering method

參考文獻

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