Vibrational and luminescent properties of LaPO₄:Eu³⁺ with different preparation conditions

张忠举¹，时婧²，王晓燕¹，刘思达²，王昕²

1. College of Chemistry and Chemical Engineering,Ocean University of China2. Institute of Materials Science and Engineering,Ocean University of China

摘 要：Monoclinic and hexagonal LaPO₄:5 mol.%Eu³⁺ phosphors were synthesized with merely adjusting pH values of solutions by a hydrothermal method at the same synthesis temperature. The microstructure, morphology and photoluminescence of Eu³⁺-doped LaPO₄, which were influenced by different preparation conditions, were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FT-IR）, Raman spectroscopy and luminescence spectroscopy, respectively. The specimen showed monoclinic structure in strong acid solution, however, it changed into hexagonal structure in weak acid solution and strong alkali solution. The monoclinic LaPO₄:Eu³⁺ showed the longest length to diameter ratio, which was attributed to the preferential growth of [-112]. The monoclinic specimen exhibited a slight red shift in infrared spectra, Raman band positions and charge transfer（CT） compared with hexagonal specimens. Moreover, the calculated results of grain sizes, lattice parameters, full width at half maximum in Raman patterns and emission integral intensity were in good agreement with analysis results. The monoclinic specimen showed the maximal absolute luminescence quantum yield（0.4） and the second lifetime τ₂（0.52 ms）, which was accordant with red-orange emission in CIE. The ⁵D₀→⁷F₁ occupied a dominate position in hexagonal specimens, which indicated that more Eu³⁺ in the hexagonal structure were occupied inversion center of symmetry sites.

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