| Due to its advantages of small volume, high efficiency, fast response, energy saving and environment friendly, since it advent, White-LEDs have been widly applied in solid-state lighting. For national society commercial use, get white light commonly through combining blue LED chip and yellow phosphors. However, the current prepared W-LEDs usually have insufficiency of low color rendering index due to short of red light composition. Also the commercial red phosphors displays a rather low effieient emission under near-UV or blue light excitation, so research novel and efficient red phosphor is the most important problem for luminescence materials. In this treatise, the rare-earth aluminate/molybdate/oxalate with superior chemical stability were regarded as the research subjects. These excellent optical materials were synthesized by conventional material preparation methods, and their luminescent properties were disscussed detailedly. The research of this paper includes the following:1. A series of Ca4-xAl6WO16:xEu3+red-emitting phosphors have been successfully synthesized by the combustion method and characterized with X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectra (EDS) and photoluminescence (PL). The results indicated that the samples were well crystallized with irregular lamellar-like shape and belonged to the tetragonal structure and space group P4c2. Photoluminescence spectra showed that the phosphors can be efficiently excited by near-UV light and exhibited a characteristic red luminescence corresponding to the electric dipole transition5D0â†'7F2at618nm. The emission intensity of Eu3+ions in the Ca4Al6WO16(CAWO) host largely enhanced with the concentration increasing of activator (Eu3+) ion and sensitizer (Bi3+) ion, and the emission intensity reached the maximum at x=0.4and y=0.02in Ca4-x-yAl6WO16:xEu3+, yBi3+phosphor. Addition of Bi3+ions drastically improved Eu3+ions emission owing to its strong absorption of excitation energy and effectively energy transfer to Eu3+emission center. It is shown that Ca4-xAl6WO16:xEu3+phosphors are promising red-emitting candidates for near-UV LED-based solid-state lighting (SSL). 2. Eu3+activated LaMoBO6phosphors have been successfully synthesized by Pechini method. The structure, morphology and properties of photoluminescence were characterized systematically. The phosphor have strong red emission centered at about618nm under excitation of near-UV (396nm) or blue (466nm) light at room temperature and the optimum doping concentration for Eu3+is0.6mmol in1mmol matrix. The CIE chromaticity coordinate of the phosphor was close to the standard value for red. In addition, we found that a little amount of fluxes will conduce to the modification of shape and luminescence of phosphors, the best flux is NH4F, and its optimum addition is2wt%. The results indicate that the Eu3+activated LaMoBO6phosphor is a promising red emitting candidate for the application in white light-emitting diodes (W-LEDs).3. Fully concentrated Eu3+based oxalate Eu2(C2O4)3·10H2O phosphor has been successfully synthesized by an efficient surfactant-free hydrothermal method directly without further sintering treatment. It was found that in the temperature range of100-150℃, all samples were well crystallized with monoclinic structures. And the best purity of the samples produced was achieved when the temperature is150℃. The possible formation mechanisms for Eu2(C2O4)3·10H2O with different structures were put forward. The Eu2(C2O4)3·10H2O phosphors can be effectively excited by396nm light, and exhibit strong red emission around619nm. A detailed investigation on the fluorescence of products revealed that the luminescence properties are strongly correlated with the crystallinities, morphologies and sizes. |
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