臺灣博碩士論文加值系統

黃光系列之釔鋁石榴石摻雜鈰螢光粉配合藍光發光二極體的獨特性質，適合做為高效率之白光光源，開啟了白光LED 應用於照明的開端。近年來，在高功率LED的發展之下，其驅動電流愈來愈大，衍生熱管理問題，進而影響發光效率。解決之道，需同時提升轉換效率及改善熱穩定性。以磷酸鹽氧化合物( ABPO4，A=Li+, Na+, K+, Rb+, Cs+，B=Mg2+, Ca2+, Sr2+, Ba2+ )為主體晶格之螢光粉，具有共價性質之三維剛性結構，極適合載子之傳輸，且其熱穩定性相當優異。因此，使用磷酸鹽為主體晶格之螢光粉材料，為一可行且有效解決高功率白光LED熱問題之方法。
本研究選用KSrPO4之磷酸鹽結構作為主體晶格，並採用Sm作為活化劑。以微波取代傳統燒結，製備KSrPO4:Sm3+螢光粉，並探討粉體微結構、材料特性及發光特性。實驗結果顯示：以之KSrPO4:Sm3+螢光粉具有較佳之表面微結構及均勻顆粒分佈，使其可以有效地在近UV波段被激發，並發射出599 nm之紅色光。當燒結溫度提升至由1000提升至1200°C時，其微結構型態會明顯改變，且經歷尺寸會變大。當燒結溫度提升至1300°C時，會有液相燒結現象發生，因而導致晶粒不規則成長。
此外，助熔劑 (flux)也常被用來促進燒結過程並提升螢光粉的發光特性。本研究亦運用NH4Cl做為助熔劑。實驗結果顯示：添加2 wt%的NH4Cl助熔劑的KSr0.99PO4:0.01Sm3+螢光粉的發光強度會隨著燒結溫度的增加而增加，並於1150℃達到飽和。當燒結溫度提升至1200°C時，發光特性急遽降低。
最後，本研究選擇最佳條件製備KSrPO4:Sm3+紅色螢光粉，並封裝在LED。實驗結果顯示：以微波輔助燒結製備KSrPO4:Sm3+螢光粉的熱淬火溫度(T50) 為 300°C，並可順利應用於LED晶片。

Considering blue LEDs emit light with a wavelength is shorter than the green ones, it is possible to excite a suitable and intense yellow light-emitting phosphor which is complemented into the blue emission, and then a yield ideal white light is created. Out of all the phosphor LEDs involved, Ce doped yttrium-aluminate-garnet phosphor was found to be the most suitable satisfactorily tested on GaN LEDs for the production of white light. Recently, because of the high power LED growth, its driving current is increased, therefore heat problem is become a main issue, and will affect luminous efficiency. In order to overcome the above shortcomings, it is necessary to take a way to improve the conversion efficiency and thermal stability simultaneously. Regarding the heat problem, the phosphate oxide compound ( ABPO4，A=Li+, Na+, K+, Rb+, Cs+，B=Mg2+, Ca2+, Sr2+, Ba2+ ) as the host lattice of covalent nature of the phosphor with three dimensional rigid structure. The phosphate oxide is very suitable for carrier transport, and the thermal stability of the phosphate series is quite outstanding. Using phosphate as host lattice in the phosphor material can solve the thermal problem of the high power of white LED in effective way.
In this study, KSrPO4’s phosphate structure is selected as the host lattice and Sm is chosen as the flux. Instead of the traditional sintering method, KSrPO4:Sm3 phosphate is made by using microwave assisted sintering technique, and then the microstructure, material and photo-luminescent properties of phosphate are investigated. The experiment results show that KSrPO4:Sm3+ phosphors have a uniform particle size distribution, and the excitation and emission spectra of the KSrPO4:Sm3+ phosphors indicate that they can be effectively excited by a NUV LED chip, and emit mainly at the 599 nm red wavelength, when sintering temperatures was increased to 1200°C from 1000°C, significant change in the morphologies and increase in particle size. When the sintering temperature was increased to 1300°C, a liquid phase sintering results in abnormal grain growth.
Moreover, several fluxes were used to improve the sintering process and to enhance the photo-luminescent properties in phosphor. In this study, NH4Cl is also adopted as fluxes to synthesis KSrPO4:Sm3+ phosphors. The experiment result shows that the emission intensity of KSr0.99PO4:0.01Sm3+ phosphors with 2 wt. % NH4Cl flux is also enhanced when the sintering temperature climbed to 1150°C from 1050°C and the maximum degree is at 1150°C, but the photo-luminescent is decreased dramatically when the sintering temperature was increased to 1200°C.
In the last part of this study, the optimal parameter for phosphor of KSrPO4:Sm3+ red phosphate is chosen and packaged it into the LED. The experimental results presented that the thermal quenching temperature T50 of the prepared KSr0.99PO4:0.01Sm3+ phosphor is 300°C and the phosphor could be successfully applied in LED.

Abstract(Chinese).................I
Abstract(English) ...................... II
ACKNOWLEDGEMENTS....VI
Contents................... VII
Chapter 1
Introduction.............. 1
1-1 Introduction of phosphor................... 1
1-2 The structure of KSrPO4 ................... 6
1-3 Motivation of this study ...................... 7
Chapter 2 Basic theory ............ 8
2-1 Emission theory and process of the phosphor........................................... 8
2-1-1 Luminescence property of the rare earth elements......................8
2-2 Properties of phosphors .................9
2-2-1 Concentration quenching effect……………………..9
2-2-2 Thermal quenching effect………………………………10
2-3 Microwave-assisted sintering.......11
Chapter 3 Experimental procedures ................. 14
3-1 Experimental materials................. 14
3-2 Experimental procedures............ 14
3-2-1 Fabrication of KSrPO4:Sm3+ phosphors with various Sm3+ doping amount...........14
3-2-2 Fabrication of KSrPO4:Sm3+ phosphors with various sintering temperature........16
3-2-3 Fabrication of KSrPO4:Sm3+ phosphors with NH4Cl flux sintered at various sintering temperature..........17
3-2-4 Fabrication of KSrPO4:Sm3+ phosphors with various NH4Cl flux amount sintered at 1150℃………………………18
3-3 Measurement system................. 19
3-3-1 X-ray Diffraction..............................19
3-3-2 Scanning lectron Microscope......................21
3-3-3 Spectrofluorimeter.................................22
3-3-4 Electroluminescenc..................................23
Chapter 4 Results and discussions...................... 24
4-1 Effects of Sm3+ on KSrPO4:Sm3+ phosphors and their Properties....... 24
4-2 Effects of sintering temperature on KSrPO4:Sm3+ phosphors and their properties ...................... 31
4-3 Effects of sintering temperature on KSrPO4:Sm3+ phosphors with NH4Cl flux and their properties....36
4-4 Effects on NH4Cl flux amount of KSrPO4:Sm3+ phosphors and their properties ............................... 42
4-5 Effects on thermal stability of KSr0.99PO4:0.01Sm3+ phosphor ............. 47
4-6 Effects on package performance of KSr0.99PO4:0.01Sm3+ phosphor .... 51
Chapter 5 Conclusions and Future works............. 52
References ............................... 54

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