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Synthesis and atomic-level characterization of rare earth oxide nanoparticles with EELS and XAS.

机译：EELS和XAS合成稀土氧化物纳米粒子及其原子级表征。

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Rare earth doped yttria nanoparticles were synthesized with a pulsed laser ablation technique. The effects of dopant concentration, starting materials, and post-ablation processing on the luminescent and structural properties were investigated. Increasing the amount of Tb in the yttria particles from 5% to 10% decreased the luminescence, contrary to what would be expected if more luminescent species (Tb3+ ions) were being added. However, using Tb2O3 instead of Tb4O 7 as the starting material did slightly increase the luminescence intensity of the Tb3+ emission. X-ray diffraction showed that the Tb:Y 2O3 samples were a mixture of the monoclinic Y2O 3 and anorthic TbO1.81 crystal structures. For the Eu:Y 2O3 nanoparticles, annealing the powder after the ablation synthesis improved the crystallinity of the particles, decreased the luminescence emission associated with Eu3+ in a monoclinic crystal structure and increased the emission associated with the cubic structure.; Rare earth oxide (Ho2O3, Er2O3 , Tm2O3, Yb2O3) nanoparticles were synthesized in two crystal structures through a combustion process. The temperature of the hydrogen flame, regulated by the composition of the supporting gas, determined the phase of the materials; higher flame temperature produced monoclinic rare earth oxide particles, and lower temperature produced cubic particles. The set of eight rare earth oxide nanoparticles---four different compositions, each in two phases---were examined with transmission electron microscopy, electron energy loss spectroscopy (EELS), and x-ray absorption spectroscopy (XAS). The EELS and XAS oxygen K edges for the sesquioxides in both phases were systematically analyzed. This work presents the first EELS and XAS study of the uncommon monoclinic phase in these materials and the first systematic comparative study between the monoclinic and cubic phases across a range of rare earth sesquioxides. For both phases, the usual double-peak structure of the oxygen K edge typically seen for oxygen atoms tetrahedrally surrounded by metal atoms was observed, but the details of the near edge structure to differ between the two phases. These results indicate a greater peak separation for the cubic than for the monoclinic phase. A trend of increasing peak separation with increasing atomic number was also noted for both phases in the series.
机译：用脉冲激光烧蚀技术合成了稀土掺杂的氧化钇纳米颗粒。研究了掺杂剂浓度，起始材料和后烧蚀工艺对发光和结构性能的影响。将氧化钇颗粒中的Tb含量从5％增加到10％会降低发光度，这与添加更多的发光物质（Tb3 +离子）时的预期相反。但是，使用Tb2O3代替Tb4O 7作为起始原料确实会稍微增加Tb3 +发射的发光强度。 X射线衍射表明，Tb：Y 2O3样品是单斜晶Y2O 3和原晶TbO1.81晶体结构的混合物。对于Eu：Y 2O3纳米粒子，在烧蚀合成后对粉末进行退火可以改善粒子的结晶度，减少单斜晶晶体结构中与Eu3 +相关的发光发射，并增加与立方结构相关的发射。通过燃烧过程以两种晶体结构合成了稀土氧化物（Ho2O3，Er2O3，Tm2O3，Yb2O3）纳米颗粒。氢火焰的温度由辅助气体的组成决定，决定了材料的相。较高的火焰温度产生单斜晶的稀土氧化物颗粒，较低的温度产生立方晶的颗粒。用透射电子显微镜，电子能量损失谱（EELS）和X射线吸收谱（XAS）检查了八个稀土氧化物纳米粒子的集合-四个不同的成分，每个成分处于两个阶段。对两相中倍半氧化物的EELS和XAS氧K边缘进行了系统分析。这项工作是对这些材料中不常见的单斜晶相的首次EELS和XAS研究，也是对一系列稀土倍半氧化物的单斜晶相和立方相之间的首次系统比较研究。对于这两个相，观察到通常被金属原子四面体包围的氧原子所见的通常的氧K边缘的双峰结构，但是在两个相之间，近边缘结构的细节不同。这些结果表明，与单斜相相比，立方的峰分离度更大。在该系列的两个相中，还注意到随着原子序数的增加峰分离的趋势。

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