Ion Dynamics in Superionic Conductors Studied by a Spectral Hole-Burning Effect

(1)研究了Eu^<3+>掺杂CeO_2 - y_2 O_3和ZrO_2-Y_2O_3 （YSZ）体系中Eu^<3+>离子的^7F_0 -^5 D_0跃迁的光吸收光谱和发光光谱。通过对选择性激发下发光带的详细研究，得到了以下结果。在Eu^<3+> /CeO^2-Y_2O_3中，发现了三种类型的三价离子位置；没有空位的场地，最近的场地上有一个空位，第二最近的场地上有一个空位。在YSZ中，发现三价离子位点无空位，在最邻近的位点上发现一个和两个空位。(2)研究了不同成分Eu^<3+>掺杂的YSZ（ZrO_2-Y_2O_3）晶体的FLN（萤光线窄化）光谱。均匀谱线宽度在80K和300K之间与T^<2.6>成正比。由于均匀线宽和非均匀线宽具有不同的成分依赖性，R（=GAMMA_<inhomo>/GAMMA_<homo>）在某一成分处具有最大值。发现19mol%的YSZ在20K时具有最大值R=5000。这一结果表明Eu^<3+>/YSZ系统用于频域光存储器是有用的。(3)在掺2%Pr^<3+>的10mol%YSZ中，我们发现了6115A下^3H_4-^1D_2跃迁的持续空穴燃烧效应。该孔可在25K以下灼烧，4.2K时宽度为0.35GHz。假设空穴宽度等于2GAMMA_<homo>，其温度依赖性为T^<1.3>。这种温度依赖性与嵌入在聚合物中的染料分子非常相似，并且强烈表明该体系中的脱相机制涉及稀土离子与TLS（二能级系统）的耦合。持续空穴可以作为研究YSZ中缺陷中心与流动离子相互作用及微观结构的新工具。作为频域存储器的演示也将是下一步富有成果的课题。

(1) The optical absorption and luminescence spectra of ^7F_0 -^5 D_0 transition in Eu^<3+> ions are studied for Eu^<3+> -doped CeO_2 -Y_2 O_3 and ZrO_2-Y_2O_3 (YSZ) systems. From a detailed study of the luminescence bands under site selective excitation, following results are obtained. In Eu^<3+> /CeO^2-Y_2O_3, three types of trivalent ion sites are found ; the site without vacancy, with one vacancy on the nearest neighbor site, and with one vacancy on the 2nd nearest site. In YSZ, trivalent ion site without vacancy and one and two vacancies on the nearest nieghbor site are found.(2) The FLN(fluorescence line narrowing) spectra are studied in Eu^<3+> -doped YSZ(ZrO_2-Y_2O_3) crystals with various compositions. The homogeneous line width is found to be proportional to T^<2.6> between 80K and 300K. Since the homogeneous and inhomogeneous line widths have different composition dependence, R(=GAMMA_<inhomo>/GAMMA_<homo>) has a maximum value at certain composition. It is found that the 19mol% YSZ has a maximum value, R=5000, at 20K. This result suggests usefulness of the Eu^<3+>/YSZ system for a frequency domain optical memory.(3) In 10mol%YSZ doped with 2%Pr^<3+>, we found a persistent hole-burning effect for ^3H_4-^1D_2 transition at 6115A. The hole can be burned below 25K and its width is 0.35GHz at 4.2K. The hole width, which is assumed to be equal to 2GAMMA_<homo>, has a T^<1.3> temperature dependence. This temperature dependence is very similar to that of the dye molecules embedded in polymers, and strongly suggests that the dephasing mechanism in this system involves a coupling of the rare-earth ions with TLS(two level system). The persistent hole can be used as a new tool to investigate the microscopic structures and the interaction of the mobile ions with the defect centers in YSZ. A demonstration as a frequency domain memory will be also a fruitful subject as a next step.