單一粒徑次微米球形氧化物螢光粉體之製備與分析

Abstract

近年來用於新型顯示器之螢光粉體除了顏色純度、發光效率、熱及化學穩定度外，因為解析度要求的關係，粉體的尺寸(如奈米精控等級)、外形(如球形)以及粒徑分佈(窄分佈)也相形重要。在本研究中，我們亦嘗試製備出三種接近單一尺寸之球形次微米氧化物粉體，包括氧化銦(In2O3)，氧化釔(Y2O3)，及以表面鍍有氧化釔或矽酸釔之氧化矽(SiO2)，並經由摻雜稀土族(rare earth)元素以及適當之熱處理，使之成為螢光體。其中球形之氧化銦於酸鹼析出反應的同時，需藉由添加特定之羧酸(carboxylic acid)，例如檸檬酸(citric acid)才可得到，本研究深入研究合成成因，探討其反應動力學，以粉體之微結構為佐證。在球形氧化釔的例子中，於反應的同時，藉由添加銪(Eu)或鋱(Tb)產生共同析出，再經過適當的熱處理，可得到接近單一粒徑之次微米球形之螢光粉體，其粒徑分佈(dispersity)最佳可達8%。而具有紅、綠或是藍光螢光性質之光子晶體則是利用自組裝法所堆積形成之氧化矽光子晶體，在其表面上鍍膜及熱處理，形成殼核結構(core-shell)，按熱處理溫度的不同，產生連續且厚度不到10奈米之氧化釔或矽酸釔(Y2SiO5)殼。光子晶體本身的特性加強了螢光體的發光效率亦於本研究中討論之。除了球形顆粒的合成外，本研究也利用基本幾何分析以及電腦模擬的方式，得到膠體顆粒形成完美堆積之途徑。若利用特殊設計之矽晶底版，有機會得到完美無缺陷之體心正方體(Body-centered tetragonal, BCT)光子晶體。本研究經由調整前人所建立之電腦模擬工具，完成數種特定之膠體顆粒積堆模擬。

For the application of phosphors in the field of modern displays, excellent color purity, high luminescent efficiency and good temperature and chemical stability are necessary. However, recently, the size, shape and size distribution of the phosphors are getting more attention because of the necessary of high resolution and performance in fashion displays. In this study, three spherical phosphors In2O3, Y2O3, and SiO2 coated by Y2O3 or Y2SiO5 spheres in submicron scale are synthesized. The results showed that In2O3 spheres in submicron scale was obtained by acid-base precipitation method with the addition of specific di- or tri-carboxylic acids, such as citric acid. The reaction kinetics and microstructure of the In2O3 spheres have been studied and discussed. For the case of Y2O3 spheres, by doping with rear earth element (RE, such as Eu3+ or Tb3+), uniform and submicron spherical Y2O3 phosphors could be obtained. Additionally, SiO2-based photonic bandgap (PBG) crystal with photo-luminescence (PL) property was obtained as coating an Y2O3 phosphor layer on SiO2 spheres. PBG crystals with red, green, or blue emitting properties were prepared by coating Y2O3:RE on the surface of the SiO2 spheres. Depending on calcination temperature, a core-shell structure consisted of a continuous Y2O3 or Y2SiO5:Re3+ shell layer of 10 nm or less thickness was prepared. The enhancement of PL properties by PBG crystal due to band-edge effect was discussed. In addition to synthesis procedure, computer simulation was used to study the packing behavior of colloids in water system. With the aid of geometric analysis and computer simulation, body-centered tetragonal (BCT) structure was proven to be a possible structure for domain-free PBG crystal. This study modify previous computer program and simulate several colloidal packing cases.