Ag^+掺杂的立方相Y_2O_3:Eu纳米晶体粉末发光强度研究

Luminescence intensity of Ag^+ doped Y_2O_3:Eu nanocrystals

采用化学自燃烧法制备了不同Ag+掺杂浓度的Y2O3:Eu纳米晶体粉末样品([Y3+]∶[Eu3+]∶[Ag+]=99∶1∶X,X=0—3·5×10-2),以及通过退火处理得到了相应的体材料.根据X射线衍射谱确定所得纳米和体材料样品均为纯立方相.实验表明在纳米尺寸样品中随着Ag离子浓度的增加,荧光发射强度随之增加,当X=2×10-2时达到最大值,其发光强度比X=0时提高了近50%.当Ag离子浓度继续增加,样品发光强度保持不变.在相应的体材料样品中则没有观察到此现象.通过对各样品的发射光谱,激发光谱,X射线衍射图谱,透射电镜(TEM)照片和荧光衰减曲线的研究,分析了引起纳米样品荧光强度变化的原因是由于Ag离子与表面悬键氧结合,从而使这一无辐射通道阻断,使发光中心Eu3+的量子效率提高;Ag+的引入所带来的另一个效应是使激发更为有效.这两方面原因使发光效率得到了提高.

Eu^3＋ doped Y2O3 nanocrystalline and bulk powders with small content of Ag^＋ were prepared by chemical self-combustion An interesting phenomenon was observed： with an increase in Ag^＋ content the luminescent intensity of the nanosized crystal is enhanced at first and then maintains a stable level; however for the bulk powder there is no obvious change in the luminescent intensity when the Ag^＋ content is varied. The morphology and crystal structure were characterized by transmission electron microscopy （TEM） and X-ray Diffraction （XRD）, respectively. Emission spectra were measured for nano- and bulk samples. The fluorescence decay curves for all the samples, including nanosized and bulk ones, either with or without Ag^＋, were measured. It is found that the lifetime for the nanosized sample with Ag^＋is longer than that without Ag^＋, and the lifetime for the bulk sample has no change. From these experimental results wecome to the conclusion that the Ag^＋ ion may link with a suffice O^2- , which has a free bond, then the suffice unsaturated dangling bonds can be eliminated. The elimination of surfice dangling bonds may cause the increase of luminescence efficiency of Eu^3 ＋ doped nanosized Y2O3.