New Red Phosphors Based on Titanate and Borate for Flat Panel Display (FED and PDP) Applications

Alternative Title
Tian, Lianhua
Alternative Author(s)
Tian, Lianhua
일반대학원 분자과학기술학과
The Graduate School, Ajou University
Publication Year
Alternative Abstract
Field emission displays (FEDs) and plasma display panels (PDPs) are of the most promising flat-panel displays. Most available phosphors for FEDs do not have high enough luminescence efficiency at low voltages. Wide band gap semiconductive SrTiO₃host lattice with perovskite structure has been investigated for FEDs. The red luminescence intensity of SrTiO₃was enhanced remarkably by the incorporation of Li^(+) ion as [xSrTiO₃+ (1-x)Li₂TiO₃]:Pr^(3+). The enhanced luminescence is thought to result mostly from the oxygen vacancy generated by Li^(+) ion incorporation in the lattices. BaTi₄O_(9) has a pentagonal-prism tunnel structure. In BaTi₄O_(9):Pr^(3+), two emission peaks are observed at 606 nm and 630 nm which correspond to transition of ¹D₂→ ³H₄. The PL spectrum of Sr_(1-x)Ba_(x)Nb₂O_(6):Pr^(3+) shows the red emission at 608 nm. For PDPs, (Y,Gd)BO₃:Eu^(3+) is usually used as a red phosphor, which yields an orange color due to the presence of the rather intense ^(5)D_(0) → ^(7)F₁emission line at 591 nm. In order to improve the color purity, the borates which have noncentrosymmetry structure are sought in this work. Vacuum ultraviolet (VUV) excitation and photoluminescence (PL) characteristics of the Eu^(3+) ion activated borate phosphors; BaZr(BO₃)₂:Eu^(3+) and SrAl₂B₂O_(7):Eu^(3+) are studied. The excitation spectra show strong absorption in the VUV region with the absorption band edge at ca. ₂00 nm for BaZr(BO₃)₂:Eu^(3+) and 183 nm for SrAl₂B₂O_(7):Eu^(3+), respectively, which ensures the efficient absorption of the Xe plasma emission lines. In BaZr(BO₃)₂:Eu^(3+), the charge transfer band of Eu^(3+) does not appear strongly in the excitation spectrum, which can be enhanced by co-doping the Al^(3+) ion into the BaZr(BO₃)₂ lattices. The luminescence intensity of BaZr(BO₃)₂:Eu^(3+) is also increased by Al^(3+) incorporation into the lattices. The PL spectra show the strongest emission at 615 nm corresponding to the electric dipole ^(5)D_(0) → ^(7)F₂transition of Eu^(3+) in both BaZr(BO₃)₂ and SrAl₂B₂O_(7), similar to that in YAl₃(BO₃)₄, which results in a good color purity for display applications. The PL intensity has also increased by incorporating La^(3+), however the red color purity has deteriorated because of the increased centrosymmetric nature of the site with the smaller size of La^(3+) than Ba^(2+). With the incorporation of Y^(3+) into the BaZr(BO₃)₂lattice, the PL characteristics of the Eu^(3+) activator resembles that in the YBO₃lattices. The luminescence intensity is the highest with good color purity for BaZr(BO₃)₂:Eu^(3+) incorporated with both Al^(3+) (10 mol%) and La^(3+) (0.5 mol%). For lighting applications Ca₄YO(BO₃)₃:Eu^(3+) and Ca₄YO(BO₃)₃:Tb^(3+) are excellent red and green phosphors, respectively. In Ca₄YO(BO₃)₃:Eu^(3+), the excitation band appears strongly at ₂50 nm with ca. 100 nm bandwidth, and the resultant emission at ca. 611 nm. The Tb^(3+) ion in Ca₄YO(BO₃)₃also emits efficiently green at 547 nm similar to that in oxides with UV the excitation of the allowed 4f → 5d transition.

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Graduate School of Ajou University > Department of Molecular Science and Technology > 3. Theses(Master)
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