Er~(3+),Yb~(3+)共掺杂Y_2O_3纳米晶体粉末中1.5μm近红外发光增强现象的研究

用燃烧法制备了平均粒径为10和40nm的(Y0.96Er0.02Yb0.02)O3纳米晶体样品,并通过1200℃高温退火获得了同样组分的体材料样品。利用X射线衍射谱(XRD),傅里叶变换红外吸收光谱(FTIR),透射电镜(TEM)和透射电镜(SEM)照片对样品的晶体结构和形貌进行了表征。测量了不同样品980nm激发下的上转换发射光谱和近红外发射光谱。对实验结果的分析发现,随着粒径的减小,样品发射光谱中红光和近红外发射的成分增加。产生这一现象的原因是由于纳米材料具有比表面积大的特点,能够吸附更多的OH-(振动能量3200～3800cm-1),OH-数量的增加使电子从Er3+的4I11/2→4I13/2能级(能量差3600cm-1)的无辐射弛豫速率增大,这一无辐射弛豫过程减少了4I11/2上的电子布居数,使绿光发射减弱;同时增加了4I13/2上的电子布居数,使红光和近红外发射增强。40nm样品的1.5μm发射主峰强度是体材料的1.6倍,这一结果对纳米发光材料的实际应用是很有意义的。

The Enhancement of 1.5 Near Infrared Luminescence in Er3+ and Yb3+ Codoped Y2O3 Nanocrystalline

(Y0.96Er0.02Yb0.02)O3 nanocrystals of 10 and 40 nm average particle size were prepared by combustion method.And bulk materials of the same components were obtained by annealing at 1 200 ℃.X-ray diffraction (XRD),Fourier transform infrared (FTLR) spectra,transmission electron microscope (TEM),and scanning electron microscopy (SEM) were used to characterize the crystal structure and morphology of the samples.The upconversion emission spectra and NIR (near-infrared) emission spectra were measured,under 980 nm excitation.The research result indicates that as the particle size decreases,the upconversion red emission and NIR emission components increase in the emission spectra.This phenomenon is attributed to the large ratio of surface area to volume in nanocrystals.This characteristic makes the nanocrystals absorb more OH-,whose vibrational energy is 3 200-3 800 cm-1.The increase in the OH- number enhances the rate of nonradiative relaxation from Er3+4I11/2 to 4I13/2 energy level (energy gap is 3 600 cm-1).This nonradiative relaxation process depopulates the 4I11/2 level and makes the green emission weaker.Meanwhile,this process populates the 4I13/2 level and makes the red and NIR emissions stronger.The intensity of 1.5 μm main peak is 1.6 times that of bulk materials.This result has great significance in actual applications of nanophosphors.