The studies of preparation conditions on the photoluminescence properties of tetragonal structure LaVO4:Pr3+ phosphors

Autor: PENG, KANG-WEI, 彭康瑋
Rok vydání: 2018
Druh dokumentu: 學位論文 ; thesis
Popis: 106
In this study, LaVO4 was prepared by hydrothermal method and doped with different concentrations of Pr3+ ion as the luminescent center for the phosphor. The effects of the Pr3+ ion concentrations, the crystal structure and photoluminescence properties of the phosphor were investigated. In order to enhance the photoluminescence properties of LaVO4:Pr3+ phosphors, the Pr3+ ion concentration was fixed for 2 mol% and doped with different Y3+ ion concentrations. The XRD results show that the crystal structure of (La0.98-yPr0.02Yy)VO4 phosphor prepared by 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 Y3+ ion doping concentration increased. The SEM results show that the phosphor particles become smaller and inconsistent as the Y3+ ion concentrations increase. Under an excitation of 315 nm, when the Y3+ ion concentration is 3 mol%, the emission spectra of (La0.98-yPr0.02Yy)VO4 phosphors show a maximum intensity of emission peak at 607 nm which is corresponding to the 1D2→3H4 electron transition of Pr3+ ion. 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. The optimal PL intensity is obtained when Y3+ ion concentration is 3 mol%, and which is located in the white region with the CIE chromaticity coordinates of (x=0.326, y=0.266). LaVO4 phosphor powder doped with fixed Pr3+ ion concentration of 0.2 mol% and at pH=8 exhibited morphological changed and significantly improved luminescence properties. The XRD patterns show that the crystal structure keeps a tetragonal crystal structure. The SEM images show that when pH=8, the surface morphology of the phosphor powder changes from a particle to a rod and grows uniformly. At the excitation wavelength of 315 nm, it was found that when pH=8 had the strongest emission intensity, and which is located in the red region with the CIE chromaticity coordinates of (x=0.396, y= 0.228).
Databáze: Networked Digital Library of Theses & Dissertations
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