Search

Abstract: Phosphors of nanoparticles LaSrAl3O7:RE3+(REave been prepared by a sol–gel method. The structure and luminescent properties of LaSrAl3O7:Eu3+ and LaSrAl3O7:Tb3+ phosphors were characterized by X-ray diffraction and atomic force microscopy (AFM), photoluminescence excitation and emission spectra were utilized. From X-ray diffraction (XRD) patterns, it is indicated that the phosphor LaSrAl3O7 forms without impurity phase at 900°C. From atomic force microscopy (AFM) images, it is shown that the crystal size of the phosphores are about 60–80nm. Upon excitation with UV irradiation, it is shown that there is a strong emission at around 617nm corresponding to the forced electric dipole 5D0–7F2 transition of Eu3+, and at around 545nm corresponding to the 5D4–7F5 transition of Tb3+. The dependence of photoluminescence intensity on Eu3+(or Tb3+) concentration and annealing temperature were also studied in detail. [Copyright &y& Elsevier]

Selective structure and shape of Eu3+-doped monoclinic LaPO4and hexagonal LaPO4·1.5H2O nanocrystals were successfully synthesized by a hydrothermal method. It was found that the pH and temperature of the growth solution are two crucial factors in determining the structure and morphology of LaPO4nanocrystals. The properties of the Eu3+-doped LaPO4nanocrystals were characterized by XRD, SEM, TEM, XPS and UV-vis spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: The co-precipitation reaction soft chemistry method was employed to prepare fine YPO4:Dy3+ phosphor particles calcined at 950°C. Adjusting appropriate pH and introducing lithium may greatly affect the particle size of the product and further affect the luminescence intensity. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron micrograph (TEM) and photoluminescence (PL) spectroscopy. The obtained YPO4 nanocrystals appeared to be spherical with some agglomeration and their sizes ranged from 20 to 40nm. The characteristic transitions of Dy3+ due to 4F9/2→6H15/2 (blue) and 4F9/2→6H13/2 (yellow) were detected in the emission spectra. [Copyright &y& Elsevier]

Abstract: Phosphors of nanoparticles YP X V1− X O4:Dy3+ (0⩽X⩽1) have been prepared by a citrate sol–gel method. X-ray diffraction, transmission electron microscope (TEM), scanning electron microscope (SEM) and photoluminescence excitation and emission spectra were utilized to characterize the phosphors. The results of XRD showed that a solid solution formed in YP X V1− X O4:Dy3+ phosphor series from X=0 to X=1 with zircon structure. TEM and SEM studies revealed that the obtained YP X V1− X O4:Dy3+ nanocrystals appeared to be spherical with some agglomeration and their sizes ranged from 30 to 80nm. Upon short ultraviolet excitation, the optical properties of all the powder presented that the characteristic transitions of Dy3+ due to 4F9/2–6H15/2 (blue) and 4F9/2–6H13/2 (yellow) were detected. Besides this, in the system of YP X V1− X O4:Dy3+, the yellow-to-blue intensity ratio (Y/B) depended on the value of P/V greatly, with the increasing of X value and the decreased Y/B value. The phosphor found to yield white light when the value of X in the range of X=0.775–0.85, the optimum concentration for Dy3+ is 1mol% of Y in the host, and the emission intensity increased with the annealing temperature. [Copyright &y& Elsevier]

Abstract: By using metal nitrates as starting materials and citric acid as complexing agent, GdCaAl3O7:Eu3+ and GdCaAl3O7:Tb3+ powder phosphors were prepared by a citrate-gel method. Thermal analysis (TG–DTG), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM), photoluminescence excitation and emission, as well as kinetic decays were employed to characterize the resulting samples. The results of the XRD indicated the precursor samples began to crystallize at 800°C and the crystallinity increased with elevation the annealing temperature. TEM images showed that the phosphor particles were basically of spherical shape, with good dispersion about a particle size of around 40–70nm. Upon excitation with UV irradiation, it is shown that there is a strong emission at around 617nm corresponding to the forced electric dipole 5D0–7F2 transition of Eu3+, and at around 543nm corresponding to the 5D4–7F5 transition of Tb3+. The dependence of photoluminescence intensity on Eu3+ (or Tb3+) concentration and annealing temperature were also studied in detail. [Copyright &y& Elsevier]