Trivalent dysprosium (Dy3+)‐doped NaCaPO4 phosphors were synthesized by using a conventional solid‐state reaction technique. The phase and the structure of the as‐prepared powders were characterized by using X‐ray diffraction analysis and revealed that the pure NaCaPO4 formed with orthorhombic structure. The photoluminescence excitation and emission spectra were measured to characterize the luminescent properties of NaCaPO4:Dy3+ phosphors. Sharp emission peaks were observed at 482 nm (blue) and 575 nm (yellow) upon 367 nm excitation, which are attributed to the characteristic 4F9/2→6HJ (J=15/2 and 13/2) transitions of trivalent Dy3+ ions, respectively. The suitable control of the blue/yellow intensity ratio is expected to realize a white luminescent system. The lifetime of 4F9/2 level was measured by exciting Dy3+ ions at 355 nm excitation. The chromaticity coordinates were calculated from the emission spectra and analyzed with Commission International de I'Eclairage (CIE) programs and diagrams. The CIE color coordinates fall in the white light region under different ultraviolet (UV) excitations. These results indicate that NaCaPO4:Dy3+ phosphor could be a potential candidate for UV‐based white light‐emitting diodes.
Trivalent dysprosium‐doped cubic yttrium oxide (Y2O3) nanophosphors were prepared by combustion synthesis using glycine as fuel. The resulting products were characterized by Raman and FT‐IR spectra to evaluate the vibrational features of the samples. X‐ray diffraction patterns confirmed the formation of a pure cubic phase of Y2O3. The morphology and selective area electron diffraction measurements were carried out using transmission electron microscopy (TEM) and field‐emission scanning electron microscopy. From TEM, it is observed that as‐prepared particles have average crystallite sizes of around 23 nm. The luminescent and dynamic properties of Y2O3:Dy3+ were examined as a function of temperature and different concentrations of Dy3+. The luminescence study reveals that these phosphors predominantly exhibit greenish‐yellow emission due to strong 4F9/2→6H13/2 transition at 575 nm and a feeble 4F9/2→6H15/2 transition at 488 nm. These results show that the relative luminescence intensity of emission bands changes with different heating temperatures, while the greenish yellow color luminescence as well as Commission International d'Eclairage chromaticity coordinates extracted from the emission spectra were not affected significantly. The strong greenish‐yellow emission of Y2O3:Dy3+ phosphor may be useful for applications in solid‐state white lamps for general illumination purposes.
Monoclinic phase Dy 31 :Gd 2 O 3 nanophosphors were synthesized by a combustion method using glycine followed by sintering to obtain submicrometer-size phosphors. The X-ray diffraction patterns confirmed the monoclinic structure of Gd 2 O 3 :Dy 31 phosphors. The phosphors were characterized by a transmission electron microscope, Raman, Fourier transform infrared, and fluoresence spectroscopy. The sizes of the phosphor particles are in the range from nearly 35 to 93 nm. It was observed that the emission intensities are varied with the excitation wavelength and concentration. The mechanism responsible for concentration quenching was discussed. The enhancement of emission intensities was observed while increasing the sintering temperature of the phosphor. Moreover, the CIE chromaticity coordinates of Dy 31 -doped Gd 2 O 3 phosphors fall in the white light domain of the chromaticity diagram. The above characteristics indicate that these phosphors may be potential candidates for the application of near-ultraviolet-based white-light-emitting diodes.
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