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The Y 6 WO 12 double oxide materials doped individually with rare-earth ions of Tm 3+ , Tb 3+ and Sm 3+ were prepared by a sol-gel method using citric acid as a complexing agent. The morphology of the prepared samples was studied using transmission electron microscope images and the crystallinity of the sample was confirmed by selective area electron diffraction patterns. The phase of the synthesized samples was analyzed by X-ray diffraction patterns and the optical properties were studied with photoluminescence (PL) and cathodoluminescence (CL) spectra. The emissions from the doped samples exhibited their respective colors both spectrally and to the naked eye under ultraviolet light excitation. Both PL and CL emission spectra showed the same results except the variation in the intensity of emission peaks. The activation energies calculated from the temperature-dependent PL spectra showed good thermal stability of the materials. The Commission International de I’Eclairage chromaticity coordinates calculated from the emission spectra were comparable to the standard phosphor used for lighting or imaging devices. [ABSTRACT FROM AUTHOR]

The rare-earth ions (Eu 3+ , Dy 3+ ) doped Y 6 WO 12 phosphors were prepared by a citrate-based sol–gel method. The morphologies and structural properties of the as-prepared and doped samples were analyzed by scanning electron microscope images and X-ray diffraction patterns. The luminescent properties were studied by examining the excitation and emission spectra of the samples. The Eu 3+ and Dy 3+ ions doped samples exhibited their characteristic emission bands in the visible region under ultraviolet light excitation. The temperature-dependent photoluminescence (PL) properties of the samples were also investigated. The PL spectra of the synthesized samples by the sol–gel method were compared with those of the bulk sample prepared by a solid-state reaction. Similarly, the Commission International de I’Eclairage chromaticity coordinates and the decay times of Y 6 WO 12 :Eu 3+ (3 mol%) and Y 6 WO 12 :Dy 3+ (2 mol%) phosphors were studied. [ABSTRACT FROM AUTHOR]

CaLaP 3 O 10 : Dy 3+ /Eu 3+ phosphor powders were prepared by a facile sol–gel method. These samples were thermally treated at 900 °C for 6 h to get monazite type structure with monoclinic unit cell. The phase, morphology and optical properties of phosphor samples were characterized by X-ray diffraction patterns, Fourier transform infrared spectra, scanning/transmission electron microscope images, and photoluminescence excitation and emission spectra. The Dy 3+ /Eu 3+ ions co-doped samples showed warm white-light emissions with lower correlated color temperature values at higher Eu 3+ ion concentrations. The near-ultraviolet (NUV) excitation and the effective energy transfer form Dy 3+ to Eu 3+ ions can make these phosphors as potential candidates for NUV excitation based white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Tb 3+ /Sm 3+ ions co-doped Ca 2 La 8 (GeO 4 ) 6 O 2 (CLGO) phosphors are prepared by a pechini-type sol–gel technique. The nanocrystalline phosphors are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The photoluminescence emission and excitation spectra are measured for Tb 3+ , Sm 3+ ions single-doped and Tb 3+ /Sm 3+ ions co-doped phosphor samples individually. For the Tb 3+ /Sm 3+ ions co-doped samples, we can observe emission covering the entire visible region with sharp peaks in the green, orange, and red regions. As the Sm 3+ ion concentration increases, the Commission International de I'Eclairage chromaticity coordinates shift towards warm white-light region due to the energy transfer from Tb 3+ to Sm 3+ ions. This energy transfer property is clearly observable in the emission spectra under 374 nm excitation. [ABSTRACT FROM AUTHOR]

Eu 3+ /Dy 3+ ions co-doped Ca 2 La 8 (GeO 4 ) 6 O 2 (CLGO) phosphors were prepared by a pechini-type sol–gel method. The structural and morphological studies of the CLGO phosphors were carried out by measuring X-ray diffraction patterns and scanning electron microscope images. The photoluminescence (PL) spectra of the CLGO:Eu 3+ phosphor exhibited the intense red emission due to the electric-dipole transition while the CLGO:Dy 3+ phosphor showed the blue ( 4 F 9/2 → 6 H 15/2 ) and yellow ( 4 F 9/2 → 6 H 13/2 ) emissions with almost equal intensities. The Eu 3+ /Dy 3+ ions co-doped CLGO phosphor showed the improved white light by shifting towards the warm white region. The energy transfer from Dy 3+ to Eu 3+ ions was investigated by means of PL intensities. The lifetime measurements were also performed for single-doped and co-doped samples. The calculated chromaticity coordinates indicated that these phosphors may be suitable for the fabrication of near-UV excitation-based white light-emitting diodes. [ABSTRACT FROM AUTHOR]