The Synthesis And Investigation Of Spectral Properties Of Rare-earth Ions Doped Gadolinium Molybdate Phosphors

In recent years, white light emitting diodes (white-LEDs) have attracted increasing attention because of their energy-saving and environment-friendly features. What's more, they are gradually playing an important role in the lighting field at present and in the future. The white lights can be obtained via several approaches. Amongst all the approaches the light-converting-phosphor method, namely, converting the blue lights or near ultraviolet lights from GaN-based LEDs into visible lights to form white lights, is considered to be the most promising one. In this thesis, we study on the Dy3+, Tb3+ single-doped and Dy3+/Eu3+ co-doped Gd2(MoO4)3 phosphors with the aim of exploring their feasibilities of practical applications since the MoO42- can effectively absorb the near ultraviolet light and transfer its energy to rare earth ions.Dy3+, Tb3+single-doped, Dy3+/Eu3+ co-doped Gd2(MoO4)3 phosphors were prepared by a conventional high-temperature solid-state reaction method. Their crystal structures, morphology, and spectroscopic properties were characterized by using XRD, SEM, optical spectroscopy and colorimetry, meanwhile, the energy transfers between rare earths and between rare earths and hosts were also studied.Based on the analysis of the spectral properties of Gd2(MoO4)3:Dy3+ phosphors, it was found that these phosphors could be effectively excited with near ultraviolet lights, and the energy transfer from host to Dy3+ is very effective; the energy transfers between Dy3+ ions were also studied in the framework of I-H model. The energy transfer mechanism was attributed to the electric dipole-dipole interaction. The possibility for getting white lights with the phosphors was discussed, and it was found that the red component is of lack in the emission spectra.In order to improve the color rendering property of Dy3+ single-doped Gd2(Mo04)3 phosphors, The Eu3+, which can emit red light, was introduced. It was found that Eu3+ can be an energy transfer bridge between the Dy3+ and Mo-O bond according to the analyses of luminescent properties of Dy3+/Eu3+ co-doped samples. The introduction of Eu3+ can increase the energy transfer efficiency. Moreover, it was also found that the comparable emission intensities for blue, yellow and red emissions and white light emission mixed by them can be achieved by properly adjusting Eu3+ and Dy3+ concentrations.