- 學位論文
水熱合成法製備(La1-xPrx)VO4 (x = 0~0.05)螢光粉體之研究
Synthesis and photoluminescence properties of (La1-xPrx)VO4 (x = 0~0.05) phosphor prepared using hydrothermal method
摘要
本研究以水熱合成法製備LaVO4作為螢光粉主體，並摻雜不同濃度之Pr3+離子作為發光中心，觀察摻雜濃度以及退火溫度對螢光粉的晶體結構以及發光特性的影響。 製備一系列LaVO4摻雜Pr3+離子螢光粉，由XRD分析結果顯示，在水熱處理180 oC持溫16小時條件下，可得知結構為正方晶系(tetragonal) LaVO4之結構。隨著Pr3+離子摻雜濃度的增加角度向高角度偏移，沒有觀察到二次相的產生。SEM分析方面，隨著Pr3+離子濃度增加螢光粉顆粒逐漸變大且不一致。在315nm激發下，其放射光譜由Pr3+離子的1D2→3H4和3P0→3H6電子躍遷所構成，在Pr3+離子摻雜濃度為0.5 mol%時，具有最強之放射峰強度。吸收光譜圖分析顯示，200~330nm為主晶格吸收帶，在440~500nm與580~620nm為Pr3+離子特性吸收。隨著Pr3+離子摻雜量的增加，其發光位置由近白光接橙紅光再轉變為藍光。 此外LaVO4摻雜Pr3+離子螢光粉系列進行退火4小時，XRD顯示600 oC退火4小時維持著正方晶系(tetragonal) LaVO4之結構無變相，SEM分析方面，螢光粉顆粒從退火前為60nm退火後增加至80nm且粉末顆粒從有團聚的現象逐漸轉變至均勻分布，於激發波長為315 nm激發下所得之放射光譜圖。在圖中仍可觀察到在可見光區域有3個發光帶範圍，於480 ~ 520, 580 ~ 610, 610~620,能帶所組成之放射光譜，分別屬於主體本身的發光與Pr3+離子1D2→3H4, 3P0→3H6能階特性躍遷之發光，且最強的發光能帶為1D2→3H4能階躍遷，發光峰值為607 nm，其最佳Pr3+離子濃度0.005經退火後色度座標更接近白光，其座標為(x=0.299, y=0.258)。 隨著退火溫度增加結構從正方晶系(tetragonal)結構轉變為單斜晶系(monoclinic)結構其轉變溫度為650 oC，顆粒表面明顯變大，且團聚現象更為明顯 由於退火溫度的不同，發光光譜由主體本身發光與Pr3+離子之1D2→3H4, 3P0→3H6能階躍遷之發光組成轉變至由Pr3+離子特性發光的3P0→3H4, 3P0→3H5, 1D2→3H4, 3P0→3H6, 3P0→3F2組成，且隨著退火溫度的增加1D2→3H4能階躍遷發光有紅移現象，發光強度也隨之減弱。CIE色度座標觀察出還是以退火溫度為600 oC時有最強發光其色度座標更近白光區。
並列摘要
In this study, LaVO4 was prepared by hydrothermal method to be the host material and doped with different concentrations of Pr3+ ion as the luminescent center for the phosphor. The effects of the Pr3+ ion concentrations and the annealing temperatures on the crystal structure and photoluminescence properties of the phosphor were investigated. Preparation of a series of LaVO4:Pr3+ phosphor, the XRD results show that the crystal structure of (La1-xPrx)VO4 phosphor performed using the hydrothermal method at 180°C for 16 h can be attributed to the tetragonal structure of LaVO4, and no secondary phases appear when the Pr3+ ion doping concentration increased. The SEM results show that the phosphor particles become larger and inconsistent as the Pr3+ ion concentrations increase. The Absorption analysis show that an absorption band between 200 ~ 330 nm is due to the lattice absorption, and the Pr3+ ion 4f-5d characteristic transition is located between in the 440 ~ 500 nm and 580 ~ 620 nm region. Under an excitation of 315 nm , the emission spectra show some emission bands appear which were corresponding to the 1D2→3H4、3P0→3H6 electron transition of Pr3+ ion, and the strongest emission appear when the Pr3+ ion concentration is 0.5 mol%. The CIE chromaticity coordinates varied from white light region to orange-red and then shift to blue region as the Pr3+ ion concentration increased. For Pr3+ ion-doped LaVO4 phosphor annealed at 600oC for 4 h, the XRD results show that the crystal structure keeps a tetragonal crystal structure. The SEM results show that phosphor particles were increased from 60 nm to 80 nm after annealing process, and the surface morphology gradually changed from reunion to uniform distribution. By 315 nm direct excitation, the main emission band still retains a series of LaVO4 doped with Pr3+ ion phosphor characteristics, belonging to the host luminescent, and the 1D2→3H4, 3P0→3H6 electron transition of the Pr3+ ion, respectively. When the Pr3+ ion concentration is 0.5 mol%, It possesses the strongest emission behavior, and is located in the near white light region with a CIE chromaticity coordinates of x=0.299, y=258. When annealing temperature increased, the crystal structure changes from a tetragonal to a monoclinic structure, and the surface morphologies of particle significantly larger and the reunion is more obvious. The emission spectra show the host luminescent gradually disappear, and the luminescence compositions change to the characteristic transition luminescence of Pr3+ ion corresponding to the 3P0→3H4, 3P0→3H5, 1D2→3H4, 3P0→3H6, 3P0→3F2 electron transition. It can be observed that the comparison to the monoclinic structure, tetragonal structure LaVO4 is a superior host material which possesses a higher luminous intensity.