The Synthesis And Investigation Of Spectral Properties Of Rare-earth Ions Doped Tri-color ALn（MoO₄）₂ Phosphors

In recent years, rare earth doped tricolor phosphors have attracted increasing attention of research because of their energy-saving, environment-friendly, high efficiency,high color rendering features. Therefore, these phosphors have a great applications in such fields as the lighting, display, detection and many other fields. Several molybdate compounds containing alkali metal and rare earth elements were used as host materials in this thesis. ALn(MoO4)2 is an efficient host materials for luminescence materials due to their high crystallographic anisotropy and excellent thermal and chemical stabilities, and the MoO42- can effectively absorb the near ultraviolet lights and transfer their energies to rare earth ions. At the same time, we respectively chosen Sm3+, Er3+, Tm3+as red, green, blue luminescence centers in this thesis, since they have many advantages such as low cost, ease of synthesis, great color saturation etc.High-temperature solid-state reaction method was used to prepare the rare earth ions doped molybdate phosphors. The crystal structures and spectroscopic properties of the phosphors were characterized by using XRD and fluorescence spectroscopy. From the obtained experimental results, it was found that the optimal host for Sm3+to achieve maximum luminescent intensity is KLa(MoO4)2, the optimal host for both the Er3+ and Tm3+is the same as NaLa(MoO4)2,.meanwhile, the energy transfers between rare earths and between rare earths and hosts were also observed. We studied on the relationship between the ion doping concentration and the’crystal structure and luminescence properties of the samples, and the change in fluorescence lifetime. Moreover, it was found that the optimum doping concentration of Sm3+is 3 mol%, and the optimal doping concentration of Er3+is 5 mol%.Based on the analysis of the spectral properties of the phosphors, it was found that red emission with maximum at 646 nm for Sm3+ is 4G5/2â†'6H9/2 transition, the green emission with maximum at 553 nm for Er3+is 4S3/2â†'4I15/2 transition, and the blue emission with maximum at 453 nm for Tm3+is 1D2â†'3H4 transition. From the obtained results, it can be confirmed that Sm3+, Er3+and Tm3+are good red, green and blue luminescence centers for molybdates. These phosphors could be effectively excited with near ultraviolet lights, and the energy transfers from molybdate host to these luminescence centers are very effective. When doping concentration of ions is high fluorescence concentration quenching will happen. At the same time, the doping concentration has effect on the luminescence properties and fluorescence lifetime of the rare earth ions doped molybdates.