纳米LaPO4：Eu的凝胶网格法制备及发光特性

用凝胶网格沉淀法,以明胶为分散介质,成功制备了铕掺杂的磷酸镧纳米颗粒,所需装置简单,实验条件适中.通过透射电子显微镜观察到制得的纳米颗粒粒径均匀,分散性良好.用X射线粉末衍射仪对其结构进行了表征,实验表明:LaPO₄属单斜晶系,独居石结构,600℃煅烧2h完全晶化.研究了不同煅烧温度、时间及不同铕含量对LaPO₄:Eu纳米粒子发光性质的影响.光谱数据表明:随着铕含量的增加或煅烧温度的升高,激发峰及各个发射峰的强度都增强,但264nm处的宽带峰强度随铕含量的增加变化较小,且红移了5.3nm;850℃时,煅烧0.5h发光强度最强,随着煅烧时间的延长发光强度反而减弱.

Preparation and Luminescence of Eu3+- doped LaPO4 Nanoparticles by Gel-network Precipitation Method

Recently,the study of nanometric luminescent materials has become of great interest.First,the microstructural characteristics of the phosphors,such as the size or the surface properties of the grains,play an important role in the efficiency of luminescent devices.Second,new developments such as electroluminescent devices,or biological labels imply the developments of new phosphors whose properties can be managed at the nanometric scale.So it is very exigent to develop a process that can produce particles having controlled characteristics such as morphology,composition and size for good luminescent characteristics.The choice of lanthanum phosphate was made because of the excellent luminescent properties of the bulk matrix when doped with Eu³⁺.A new gel-network precipitation method was presented to synthesize the precursor of LaPO₄:Eu nanoparticles,based on the use of lanthanide salts and(NH₄)₂HPO₄ in water along with gelatin used as the disperser.Then products with nicer luminescence were successfully obtained under mild calcining conditions.TEM images showed that the nanoparticles are basically monodisperse,and have good homogeneity with an average diameter of 50 nm.The Eu³⁺-doped LaPO₄ phosphor was characterized by powder X-ray diffraction.According to our measurements with XRD,the products belong to monoclinic monazite type,it is consistent with space group P21/n.The excitation and emission spectra were measured.Under 396 nm radiation excitation,the emission spectra of LaPO₄:Eu consists of the sharp line emissions in the range of 500～720 nm from the transitions of electrons in 4f shell of Eu³⁺.The main peak at 592 nm can be attributed to the ⁵D₀→⁷F₁ transition of Eu³⁺.The excitation spectra of Eu^{3+ 5}D₀→⁷F₂ transition emission have two parts,the wide band at 264 nm and the sharp line at 396 nm.The wide band includes both charge transfer excitation of PO^3-₄ and charge transfer excitation of Eu³⁺,while the sharp line originate from Eu³⁺ f-f electron transitions,which indicate that there is energy transfer from host lattice to activator in the process of luminescence.The luminescence data indicate the optimum condition for heat-treatment of the precursor was at 850℃ for 0.5 h.The effects of different content of Eu³⁺ on the luminescence of LaPO₄:Eu nanoparticles were also investigated,and the(results)show that luminescence intensity is enhanced with the increasing of Eu³⁺ content.