铕(Ⅲ)掺杂含氧磷酸镧纳米晶的燃烧法合成及其发光性质

Photoluminescence Properties of La_3PO_7∶Eu^(3+) Nanoparticles Synthesized by a Combustion Method

采用燃烧法合成了新型红色纳米发光材料La3PO7∶Eu3+,并用X射线粉末衍射对其结构进行了表征。XRD分析证实样品La3PO7为单斜相。测定了其激发光谱和发射光谱,光谱数据表明:对应于Eu3+的5D0→7F2跃迁的发射强度远大于5D0→7F1跃迁的发射强度,La3PO7∶Eu3+形成红色发光材料。推测是由于基质结构的不对称性,Eu3+在基质La3PO7中占据非对称中心的格位所致。在不同温度下退火后,发现退火温度越高,Eu3+的5D0→7F2跃迁辐射越强,表明样品结晶越好。

Eu^3＋ -doped oxyphosphate （La3PO7 ） nanoparticles were synthesized by a straightforward combustion method. The synthesis procedure is similar to that of preparing oxide nanomaterials by the combustion method, but here （NH4）2HPO4 is used in producing phosphate nanoparticles. Firstly, La（ NO3 ）3 was prepared by putting appropriate molar rate La2O3 （ 1.5 mmol） and Eu2O3 into the thin HNO3, stirring to a transparent solution. Excess water was evaporated and made it condensed while heating to obtain the solid La（NO3 ） 3. Then, put into 10 mL thin HNO3. At the same time, 0. 1321 g （ NH4） 2HPO4 and 0. 270 3 g Glycine were dissolved in deioned water （10 mL）. Thirdly, the solution of （NH4 ）2HPO4 and glycine were added into that of the La（ NO3 ） 3 with vigorous stirring. The precursor solution was formed. Then, the precursor solution was heated until the white foam was obtained. The reaction took place in a few minutes and all the reactions happened in a wide-mouth beaker. A monoclinic lattice was verified in them by the investigation of X-ray diffraction （XRD）. In the emission spectra of Eu^3＋ , the ^5D0→^7F0 transition is often observed when Eu^3＋ is in low site symmetry because it is forbidden based on the group theory. The ^5D0→^7F1 transition is parity-allowed magnetic dipole transition, which is slightly affected by the symmetry of the Eu^3 ＋ site. The ^5D0→^7 F2 transition ^5D0→^7F2 transition of Eu^3＋ ions and revealed the Eu^3＋ ions occupied asymmetric sites in the oxyphosphate host. After annealing at different temperatures from 400 ℃ to 1 200 ℃, we found that the higher the annealing temperature, the better the samples crystallized and the bigger the intensity ratio of I（^5D0-^7F2）/I（^5D0-^7F1）. In comparison with LaPO4： Eu^3＋, an orange phosphor with stronger ^5D0→^7F1 emission, La3PO7 ： Eu^3＋ has prominent red luminescence under the same excitation and maybe become a promising red phosphor for PDPs and Hg-free fluorescent lamp in the future.