Uniform monoclinic monazite structure LaPO4:Eu3+ hollow spheres were s ynthesized via an attractive hydrothermal method owing to the higher yield and s implicity.Photoluminescence and Raman spectra of the sample were ...Uniform monoclinic monazite structure LaPO4:Eu3+ hollow spheres were s ynthesized via an attractive hydrothermal method owing to the higher yield and s implicity.Photoluminescence and Raman spectra of the sample were investigated u nder high pressure up to 26 GPa using diamond anvil cells.At ambient pressure,the sample exhibited same luminescent properties with that of bulk monazite LaPO 4:Eu3+.With the increase of pressure,the emission intensity of Eu3+ decreased and the half-widths of transition lines increased,while emission peaks showed a red shift toward longer wavelengths due to increase in crystal-field strength.No phase transformation appeared before amorphization for monoclinic LaPO4:Eu3+ hollow spheres,which was confirmed based on the analysis of high pressure Raman spectra.The large surface energy of hollow spheres was proposed to prevent the occurrence of phase transformation.展开更多
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 photo...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, respec-tively. 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 mono-clinic specimen showed the maximal absolute luminescence quantum yield （0.4） and the second lifetimeτ2 （0.52 ms）, which was ac-cordant with red-orange emission in CIE. The5D0→7F1 occupied a dominate position in hexagonal specimens, which indicated that more Eu3＋ in the hexagonal structure were occupied inversion center of symmetry sites.展开更多
基金Project supported by the Youthfund Project of University of Science and Technology of China (KA2340000007)
文摘Uniform monoclinic monazite structure LaPO4:Eu3+ hollow spheres were s ynthesized via an attractive hydrothermal method owing to the higher yield and s implicity.Photoluminescence and Raman spectra of the sample were investigated u nder high pressure up to 26 GPa using diamond anvil cells.At ambient pressure,the sample exhibited same luminescent properties with that of bulk monazite LaPO 4:Eu3+.With the increase of pressure,the emission intensity of Eu3+ decreased and the half-widths of transition lines increased,while emission peaks showed a red shift toward longer wavelengths due to increase in crystal-field strength.No phase transformation appeared before amorphization for monoclinic LaPO4:Eu3+ hollow spheres,which was confirmed based on the analysis of high pressure Raman spectra.The large surface energy of hollow spheres was proposed to prevent the occurrence of phase transformation.
基金supported by the National Natural Science Foundation of China(51172217)
文摘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, respec-tively. 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 mono-clinic specimen showed the maximal absolute luminescence quantum yield （0.4） and the second lifetimeτ2 （0.52 ms）, which was ac-cordant with red-orange emission in CIE. The5D0→7F1 occupied a dominate position in hexagonal specimens, which indicated that more Eu3＋ in the hexagonal structure were occupied inversion center of symmetry sites.
