| Yttrium aluminum garnet (Y3Al5O12, YAG) have been widely applied to the host of laser and luminescence materials as result of its physical and chemical stability. The YAG-based luminescence materials doped by rare earth (RE) ions in particular, have been paid more and more interests and attentions of research due to its unique specifications.The indium-substituted YAG phosphors were our focus in this work. In order to study the factors influencing the luminescence properties or the preparation technology, a series of RE ions doped yttrium aluminum indium garnet (YAIG) have been successfully synthesized by using the co-precipitation method. Comparison between YAG and YAIG, differences in both the crystalline phase and photoluminescence properties were investigated respectively. Results are as follows:(1) The method of co-precipitation was used to synthesize Y3-x(Al1-yIny)5O12:Cex3+yellow phosphors. Furthermore, XRD and XPS were also utilized to analyze the structures and formation of phosphors. The results indicated that precursors of the above samples inclined to crystallization when at a temperature above900℃. Also the XRD patterns and XPS data exhibited that the phase formation did not change in the YAG even with the substitution of In3+for Al3+. The excitation and emission spectra of Y3-x(Al1-yIny)5O12:Cex3+phosphors were assigned peaking at around460nm and525nm, respectively. The maximum photoluminescence corresponded to15%concentration of Ce3+or In3+, revealing the luminescent intensity relying on the dopants concentrations. Meanwhile, the substitution of In3+for Al3+in YAG caused a blue shift effect of the emission peak.(2) The Y3-x(Al1-ylny)5O12:Eux3+white phosphors were prepared by using the co-precipitation method and sintered at1000℃. From this procedure, we obtained pure phase powders with homogenous particle size in nano-scale. From the assignment of the fluorescent spectra, the excitation and emission spectra of Y3-x(Al1-yIny)5O12:Eux3+phosphors were centered at around393and593nm, respectively. The optimized dopant concentration of Eu3+and In3+were20%and10%repectively. The crystal lattice would expand and become more stabilization along the increasing of In3+doping concentration, while the relative intensities of the phosphors would lower with the weakening of the crystallization degree.(3) Pure phase Y3-x(Al1-yIny)5O12:Hox3+powders have been prepared by co-precipitation method. The experimental results showed that the most effective excitation and emission of Y3-x(Al1-yIny)5O12:Hox3+phosphors centered at452nm and540nm, respectively. The concentration of15%or5%for Ho3+or In3+, corresponded to the maximum luminescence intensity. In addition, concentration quenching occurred when the doping concentrations of Ho3+increased. According to the calculation, the critical distance of energy transfer of Ho3+ions in YAIG was1.41nm. Similarly the relative luminescence intensities of the phosphors decreased as the crystallization was weakened.In conclusion, based on the comparison between phosphors from co-precipitation and high temperature solid state reaction methods, it is found that co-precipitation method could help to effectively reduce the calcination temperature, as well to easily obtain the pure phase ultrafine powders. The Ce3+, Eu3+or Ho3+-doped YAIG phosphors prepared by the co-precipitation method truly possessed the pure phase sturctures, but presenting obviously different luminescent properties even with the same YAG host. There existed a blue shift in emission spectra of the indium-substituted YAG:Ce3+, but no significant changes for both of the two ions doping of Eu3+and Ho3+, which could be attibuted to the special5d'4f transition of Ce3+, while the transition between only f'f configuration for Eu3+or Ho3+. In addition, concentration quenching was observed to the three phosphors along with the increase of RE ions concentration, whilst the crystallization and the luminescence intensities lowered with respect to the increase of In3+doping concentration. |
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