Eu3+或Tb3+掺杂Y2O3纳米材料紫外激发光谱

采用燃烧法制备了不同Ln³⁺(Ln=Eu或Tb)掺杂浓度和不同平均粒径的Y₂O₃:Ln纳米晶体粉末和体材料样品。研究发现随着粒径的减小,Y₂O₃:Eu电荷迁移带的位置发生红移;并且,由于存在于近表面低结晶度环境中的Eu³⁺数量的增加,小粒径样品(5nm)的电荷迁移带还向长波方向发生了明显的展宽。实验中还观察到Y₂O₃:Tb纳米晶激发谱中4f5d(4f⁸→4f⁷5d¹)跃迁吸收对应激发峰(带)的谱线形状随样品粒径变化存在较大的差异,这是由于Tb³⁺存在于近表面的低结晶度和颗粒内部的高结晶度两种不同环境中,Tb³⁺的4f5d跃迁在两种环境中对应的吸收峰位置不同,当样品粒径发生变化时Tb³⁺处于两种环境中的比例随之变化,造成相应吸收跃迁对应的激发峰(带)强度发生变化,并改变了激发谱的谱线形状。实验中还发现,随着Tb³⁺(或Eu³⁺)浓度的减小,Y₂O₃基质激子跃迁吸收的激发峰对比4f5d跃迁(或电荷迁移带)激发峰的相对强度随之增强。

Study on UV Excitation Spectra of Eu3+ or Tb3+ doped Y2O3 Nanomaterials

Y₂O₃:Ln nanocrystals with different Ln³⁺(Ln=Eu or Tb) doping concentrations and average sizes were prepared by chemical self-combustion. And the bulk materials of corresponding doping concentrations were obtained by annealing at high temperature. The emission spectra, excitation spectra and X-ray diffraction spectra of Y₂O₃:Ln nanocrystals and bulk materials were measured. The research indicated that under the effect of quantum confinement effect and surface effect, the Y₂O₃:Eu charge transfer band red-shifted clearly while the particle size decreased. Furthermore, the charge transfer band of the small size particles (8 nm) clearly broadened towards the long wavelength, this was attributed to the increase of the amount of Eu³⁺ ions existing in low crystallization degree environment close to the surface. The study also indicated that the shape of excitation peaks (bands) corresponding to the 4f5d transition absorption of Tb³⁺ in the excitation spectra of Y₂O₃:Tb nanocrystals changed a lot with the variety of the particle size. This is because that the Tb³⁺ ions exist in two very different local environments:the low crystallization degree environment close to the surface and the high crystallization degree environment inner the particles. The absorption peaks of 4f5d transition were different in the two environments. The Tb³⁺ ions ratio in the two environments changs with the variety of the particle size. So the intensity of corresponding excitation peaks (bands) changed and the shapes of the excitation spectra changed. By comparing the excitation spectra of different doping concentrations, it can be found that with the increase of Tb³⁺(or Eu³⁺) concentrations, the relative strength of the Y₂O₃ exciton transition absorption excitation peak to the 4f5d transition (or charge transfer band) excitation peak decreased. The excitation efficiency of Y₂O₃ exciton absorption band is very low when the doping concentrations of the luminescent centers were higher. But the excitation efficiency of Y₂O₃ exciton absorption band increased when the doping concentrations were quite low.