Yb3＋/Tm3＋ 共掺杂的钨酸镉纳米晶发光性能的研究

Research on Luminescence Properties of CdWO4∶Yb3+/Tm3+

本文采用水热法制备了稀土离子Yb3＋／Tm3＋共掺杂的钨酸镉纳米晶。运用X-射线粉末衍射、场发射环境扫描电子显微镜和光谱分析对制备的样品的结构和发光性能进行了表征。根据XRD图谱可知,钨酸镉为单斜晶系，晶粒平均尺寸在28nm左右。从ESEM图片可明显看出，钨酸镉呈纳米棒结构。直径在30nm左右,长径比在5-8之间。利用980nm半导体激光器激发钨酸镉纳米晶得到样品的发射光谱，存在一个较强的蓝光发射，发光峰位于481nm，对应于Tm3＋ 的 ^1G_4→^3H_6 能级的跃迁，分析了Tm3＋／Yb3＋离子共掺体系的发光机制。讨论了发光强度随稀土离子浓度的变化,当Tm3＋离子的掺杂浓度在2mol％，Yb3＋／Tm3＋物质的量浓度比C_Tm3＋/C_Yb3＋=10时 钨酸镉纳米晶的发光强度最强。根据泵浦功率与发光强度之间的关系．可知处于481nm的蓝光发射属于三光子过程，由发光强度与掺杂浓度之间的双对数衰减曲线可知，引起蓝光发射源于Tm3＋的电偶极跃迁。

In this paper, the CdWO4 nano-erystal co-doping with Yb3＋/Tm3＋ ions was synthetized by hydrothermal method. The luminescence properties and structure of the sample were measured by X-ray powder diffractions （XRD）,field emission scanning environmental electron microscope （ESEM） and spectral analysis .And the CWO was monoclinic system with the mean size of 30 nm. It could be obtained from the image of ESEM that the structure of CWO was nano-rod with the diameter of 30 nm and the length-diameter ratio was between 5 and 8. The emission spectra were obtained when it was excited by 980 nm semi-conductor laser. There was a strong blue emission peak and the value was 481nm which was due to the transition ^1G_4→^3H_6 of Tm3＋. The mechanism of Tm3＋/Yb3＋ co-doped system was also studied. The concentration of rare earths could influence the intensity of the blue emission. The strongest peak was obtained when the concentration of Tm3 ＋ was 2mol% and the concentration ratio of Yb3＋/Tm3＋ was 10：1. According to the relationship between pump power and luminescence intensity, the emission of blue peak was three photons absorption process. It can be determined from the curve of lg（I/C）-lg（C） that the strong emission band at 481 nm belongs to electric dipole transition.