ABSTRACT
Microstructures of Ca0.5Y(1-x)(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors were prepared via the solid-state reaction method. X-ray diffraction, scanning electron microscopy and photoluminescence were used to characterize the prepared phosphor samples. The results reveal that the phosphor samples have single phase scheelite structures with tetragonal symmetry of I41/a. The down/up conversion photoluminescence of the Ca0.5Y(1-x)(WO4)2:xLn(3+) (Ln=Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors properties reveal characteristic visible emissions. The energy transfer process, fluorescence lifetime and color coordinates are discussed in detail. Furthermore, the phosphor Ca0.5Y(1-x)(WO4)2:xPr(3+) co-doped with alkali chlorides shows the enhancement of luminescence, which was found in the sodium chloride co-doped powder phosphor. The photometric characteristics indicate the suitability of the inorganic powder phosphors for solid-state lighting and display applications.
ABSTRACT
Single crystalline Eu(3+) doped yttrium oxysulfide (Y(2)O(2)S) nanocrystals, nanosheets, nanobelts, nanotubes, nanorods and nanowires have been successfully prepared via precursors of Y(OH)(3) nanostructures in high yields and purities by a convenient hydrothermal method under mild conditions. Comprehensive structural, morphological and spectroscopical studies have been carried out on the nanometre scale. The as-prepared samples are characterized using X-ray photoelectron spectra (XPS), to investigate the elementary states on the surfaces. A significant shift (approximately 0.22-0.36 eV) in the optical spectra of the Y(2)O(2)S:Eu(3+) system corresponding to the fundamental absorption and charge transfer bands, respectively, with respect to the bulk counterpart. The zero and one-dimensional (1D) nanostructures are good candidates for investigating size-induced opto-electronic properties of functional oxysulfides. In order to identify the origin and nature of the electronic transitions observed in the visible region, the photo-induced impedance measurements have been extended to the zero and 1D nanostructures.
ABSTRACT
Zinc oxide (ZnO) nano thin films have been deposited by the chemical double-dip technique using aqueous ZnSO4 and NaOH solutions. The ZnO films were characterized in terms of surface morphology by x-ray diffraction, energy-dispersive x-ray analysis (EDX), the use of a scanning electron microscope (SEM) and atomic force microscope (AFM) for surface morphology. The films exhibited a smooth morphology. The chemical states of oxygen and zinc in the ZnO nano thin films were also investigated by x-ray photoelectron spectroscopy (XPS). In the present investigations, highly textured ZnO thin films with a preferential (002)-orientation were prepared on glass substrates. The deposition conditions were optimized to obtain device-quality films for practical applications.
