Rosa Ieda L V, Marques Ana Paula A, Tanaka Marcos T S, Melo Dulce M A, Leite Edson R, Longo Elson, Varela José Arana
LIEC-CMDMC, DQ, Federal University of São Carlos, Via Washinton Luiz km 235, CEP 13565-905, São Carlos, Sao Paulo, Brazil.
J Fluoresc. 2008 Mar;18(2):239-45. doi: 10.1007/s10895-007-0195-z. Epub 2007 Dec 20.
In this work Ba(0.99)Eu(0.01)MoO(4) (BEMO) powders were prepared by the first time by the Complex Polymerization Method. The structural and optical properties of the BEMO powders were characterized by Fourier Transform Infra-Red (FTIR), X-ray Diffraction (XRD), Raman Spectra, High-Resolution Scanning Electron Microscopy (HR-SEM) and Photoluminescent Measurements. XRD show a crystalline scheelite-type phase after the heat treatment at temperatures greater than 400 degrees C. The ionic radius of Eu(3+) (0.109 nm) is lower than the Ba(2+) (0.149 nm) one. This difference is responsible for the decrease in the lattice parameters of the BEMO compared to the pure BaMoO(4) matrix. This little difference in the lattice parameters show that Eu(3+) is expected to occupy the Ba(2+) site at different temperatures, stayed the tetragonal (S(4)) symmetry characteristic of scheelite-type crystalline structures of BaMoO(4). The emission spectra of the samples, when excited at 394 nm, presented the (5)D(1)-->(7)F(0, 1 and 2) and (5)D(0)-->(7)F(0, 1, 2, 3 and 4) Eu(3+) transitions at 523, 533, 554, 578, 589, 614, 652 and 699 nm, respectively. The emission spectra of the powders heat-treated at 800 and 900 degrees C showed a marked increase in its intensities compared to the materials heat-treated from 400 to 700 degrees C. The decay times for the sample were evaluated and all of them presented the average value of 0.61 ms. Eu(3+) luminescence decay time follows one exponential curve indicating the presence of only one type of Eu(3+) symmetry site.
在这项工作中，首次通过复合聚合法制备了Ba(0.99)Eu(0.01)MoO(4)（BEMO）粉末。通过傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、拉曼光谱、高分辨率扫描电子显微镜（HR-SEM）和光致发光测量对BEMO粉末的结构和光学性质进行了表征。XRD显示在温度高于400℃热处理后为白钨矿型晶体相。Eu(3+)的离子半径（0.109nm）低于Ba(2+)（0.149nm）的离子半径。这种差异导致BEMO的晶格参数相较于纯BaMoO(4)基体有所减小。晶格参数的这种微小差异表明，Eu(3+)预计在不同温度下占据Ba(2+)位点，保持BaMoO(4)白钨矿型晶体结构的四方（S(4)）对称特征。当在394nm激发时，样品的发射光谱分别在523、533、554、578、589、614、652和699nm处呈现出(5)D(1)-->(7)F(0, 1和2)以及(5)D(0)-->(7)F(0, 1, 2, 3和4)的Eu(3+)跃迁。与在400至700℃热处理的材料相比，在800和900℃热处理的粉末发射光谱强度显著增加。对样品的衰减时间进行了评估，所有样品的平均值为0.61ms。Eu(3+)发光衰减时间遵循一条指数曲线，表明仅存在一种类型的Eu(3+)对称位点。
