矽酸鍶與氧化釔螢光材料之改質及特性分析

Modification and Characterization of Strontium Orthosilicate and Yttrium Oxide Phosphors

巫柏奇(Po-Chi Wu)

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(2005年)

https://doi.org/10.6342/NTU.2005.01715

摘要

矽酸鍶(Sr2SiO4:Eu2+)由於可以提供在UV/Blue區間的寬廣吸收帶，因此提供一個以GaN晶片為基礎產生白光新的螢光粉應用方向。由熱分析及結晶繞射圖譜可以確定其生成機制是由擴散所控制; 由Brounshtein -Ginstling 模型計算出其活化能為139.6 kJ/mol。利用檸檬酸及乙二醇進行溶膠-凝膠反應合成均勻分散的Sr2SiO4:Eu2+螢光粉。藍綠光是由處於Sr(I)位置的Eu2+經由f-d能階轉換產生，而黃光則由Sr(II)位置的Eu2+所產生。此外，由黃光放射峰所模擬的激發光譜也較藍光放射峰模擬的激發光譜更為寬廣，暗示著Sr(II)可以在晶格內提供較大的晶場;當Eu2+的濃度增加時，黃光的放射峰最主導整個發光現象。在適當的條件下合成下會產生最強螢光強度與粒徑約150奈米的均勻分散Sr2SiO4:Eu2+螢光粉。

紅光螢光粉（Y2O3:Eu3+）的合成與改質被研究。研磨會將缺陷導入晶格內，使用溶膠凝膠法合成的Y2O3:Eu3+奈米粉體具有較強的螢光強度和結晶性。於1200℃鍛燒下，Eu3+相對於其他鍛燒溫度會有更不對稱的環境，因此會有最強的611 nm的放射峰。當鋰離子加入螢光粉內會有較強的結晶性，放射強度與更均勻的粒子型態;這是當鋰離子進入晶格內產生的氧缺陷會下降晶體裡的對稱性，造成增加electric-dipole的5D0→7F2能量轉換之放射峰。當導電層氧化錫包覆於螢光粉表面，可以從CL光譜中可以發現：在高電流密度操作下，未包覆導電層的螢光粉亮度很快就達到飽和;此時，包覆氧化錫的Y2O3:Eu3+螢光粉亮度依然持續增加，因此暗示了導電層可以有效地移除電荷於螢光粉表面，造成發光效率提高。

關鍵字

螢光粉 ； 白光二極體 ； 場發射顯示器

並列摘要

Strontium orthosilicate (Sr2SiO4:Eu2+) provides the broadband absorption in UV/Blue region, giving rise to a new phosphor approach for application of GaN-based white LEDs. From the TG/DTA and XRD analysis, the formation of Sr2SiO4 is confirmed to be governed by diffusion controlled mechanism. According to the Brounshtein-Ginstling model, the activation energy is suggested to be 139.6 kJ/mol. A sol-gel process employing citric acid and ethylene glycol as polymerizing agent was developed for synthesizing well-dispersed Sr2SiO4:Eu2+ phosphors. The blue-green band originates from the f-d transition of the Eu2+ ion on the Sr(I) site. On the other hand, the emission of the Eu2+ ion on the Sr(II) site is identified as the yellow band. The excitation spectra monitored at the yellow band also showed broader excitation range than that monitored at blue-green band, implying large crystal field provided by Sr(II) site. With increase of europium concentration in Sr2SiO4, the yellow broadband emission will be more dominate. Sr2SiO4:Eu2+ synthesized at the appropriate condition showed the enhanced luminescent intensity and well dispersed particles with grain size around 150 nm.

The synthesis and modification of red oxide phosphors (Y2O3:Eu3+) were investigated. The nano-sized Y2O3:Eu3+ phosphors synthesized via the sol-gel route showed the enhanced crystallinity and luminescent intensity. The europium ions of the sol-gel derived phosphors calcined at 1200℃ are in a more asymmetric environment than those calcined at other temperatures, resulting in the strongest emission intensity at 611 nm. The particles after Li+ ions doping had the advantages of enhanced the crystallinity, improved morphology, and emission intensity. It implies that oxygen defects created after Li+ ions doping would lead to lowering symmetry, resulting in enhanced the 5D0→7F2 electric-dipole emission (611 nm).Tin oxide was used as the coating material on the Y2O3:Eu3+ phosphor. At high current density, the brightness of the uncoated phosphor was quickly saturated. On the other hand, the CL intensity of SnO2-coated Y2O3:Eu3+ phosphor still increased monotonously, suggesting the removal of charge on the surface by conductive material effectively.

並列關鍵字

phosphors ； white light emitting diode ； field emission display

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