偏磷酸钛基体中四价铀离子的荧光

本文用蒸发溶液法制备了Th(PO3)4、U(PO3)4及掺杂了U4+的Th(PO3)4:U4+单晶,确定了β-U(PO3)4属于正交晶系Cmca-D2h18点群,α-U(PO3)4和Th(PO3)4都为三斜晶系P1或P1点群,给出了它们的晶格参数.测量了U(PO3)4吸收谱,和Th(PO3)4基体中U4+的激发和荧光谱.在近紫外光激发下,Th(PO3)4:U4+产生一组荧光,对应于U4+离子的6d-5f电子跃迁.270和298nm的荧光寿命约10ns,对应于电偶极跃迁.在波长为553nm绿光激发下,Th(PO3)4:U4+中四价铀的电子产生上转换效应,释放出358和533nm窄带荧光、它们属于U4+的5f-5f电子跃迁,分别对应于3P2-3H4和1I5-3H4。给出了相应的荧光和上转换效应的跃迁能级图.

LUMINESCENCE OF URANIUM (Ⅳ) ION DOPED IN THORIUM METAPHOSPHATE

A series of uranium(Ⅳ) metaphosphate U(PO3)4 and uranium (Ⅳ) doped thorium metaphosphate crystals Th(PO3)4:U4+ were grown from phosphoric acid solution by the method of solution evaporation.Th(PO3)4 and U(PO3)4 crystal compositions were checked and their crystal structures were determined. Th(PO3)4 and ar-U(PO3)4 belong to triclinic system, P1 or P1-space group.β-U(PO3)4 is orthorhombic system,Cmca-D2h18 space group. The crystallographic data are given. Absorption spectra of U(PO3)4 and the excitation spectra and fluorescence spectra of Th(PO3)4:U4+crystals have been measured at room temperature. Under the excitation with 253nm UV light, U4+ ions doded in Th(PO3)4 matrix emit a series of wide bands of violet fluorescence, which belong to 6d-5f electronic transition of activated U4+ ion. When the crystal is excited by 552nm green light, two narrow bands were found at 358nm and 533nm which might belong to 3P2-3H4 and 1l6-3H4 electronic transitions of U4+respectively. These types of transition can be explained by up-conversion mechanism. The radiation sheme of U4+doped in Th(PO3)4 are given. The fluorescence lifetime of 270nm and 298nm emission of Th(PO3)4 :U4+ crystals is only about ions. This means that the fluorescent emission is responsible for electric dipole transition,