玻璃基和粉末烧结衍生的Al-Nd共掺杂锆石的晶体结构,Inorganic Chemistry

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玻璃基和粉末烧结衍生的Al-Nd共掺杂锆石的晶体结构
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2015-07-23 00:00:00 , DOI: 10.1021/acs.inorgchem.5b00847
Chang-Zhong Liao ₁ , Kaimin Shih ₁ , William E. Lee ₂

Affiliation

锆钛矿是固定长寿命放射性核素的候选宿主。CaO-SiO ₂ -Al ₂ O ₃ -TiO ₂ -ZrO ₂ -Nd ₂ O ₃ -Na _2中的锆石基玻璃陶瓷O基质是固定act系元素放射性核素的潜在废物形式，可以提供双重障碍来固定放射性元素。但是，源自玻璃基体（玻璃陶瓷，GC）的锆石的X射线衍射图谱与通过粉末烧结（PS）制备的锆石显着不同。在本文中，详细研究了通过玻璃基体路线和粉末烧结路线生长的Al-Nd共掺杂锆石的晶体结构。准备了两个Al-Nd共掺杂锆石样品：一个样品是从CaO-SiO ₂ -Al ₂ O ₃ -TiO ₂ -ZrO ₂ -Nd ₂ O ₃ -Na _2中生长的。O玻璃基质，另一种通过粉末烧结用Ca _0.75 Nd _0.25 ZrTi _1.75 Al _0.25 O ₇组成。然后使用粉末X射线衍射（PXRD），扫描电子显微镜（SEM），透射电子显微镜-能量色散X射线光谱（TEM-EDX）和选定区域电子衍射（SAED）对样品进行表征。通过TEM-EDX确定从玻璃基质中生长的100-500 nm锆钛矿晶体的化学成分为Ca _0.83 Nd _0.25 Zr _0.85 Ti _1.95 Al _0.11 O ₇。PXRD和SAED结果表明，这两个Al-Nd共掺杂锆石沸石相在C 12 / c 1空间群中结晶。HRTEM图像和SAED结果表明，从玻璃基质中生长的锆石晶体中存在严重的堆垛层错。相反，在通过粉末烧结制备的锆钛矿晶体中发现的缺陷少得多。在Rietveld精炼过程中，首次采用分裂原子模型来构建由玻璃生长的Al-Nd共掺杂锆石结构。用Rietveld精炼辅助的同构方法用于解析通过不同方法制备的Al-Nd共掺杂锆石结构。识别阳离子位点的占用，以及Nd ³⁺的分布行为进一步调查。结果表明，严重的堆垛层错可能导致通过这两种制备方法制备的Al-Nd共掺杂锆石结构的实质性差异。

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Crystal Structures of Al–Nd Codoped Zirconolite Derived from Glass Matrix and Powder Sintering

Zirconolite is a candidate host for immobilizing long-lived radionuclides. Zirconolite-based glass-ceramics in the CaO-SiO₂-Al₂O₃-TiO₂-ZrO₂-Nd₂O₃-Na₂O matrix are a potential waste form for immobilizing actinide radionuclides and can offer double barriers to immobilize radioactive elements. However, the X-ray diffraction patterns of the zirconolite derived from the glass matrix (glass ceramic, GC) are significantly different from those prepared by powder sintering (PS). In this Article, the crystal structures of Al–Nd codoped zirconolite grown via the glass matrix route and the powder sintering route are investigated in detail. Two samples of Al–Nd codoped zirconolite were prepared: one was grown from a CaO-SiO₂-Al₂O₃-TiO₂-ZrO₂-Nd₂O₃-Na₂O glass matrix, and the other was prepared with a Ca_0.75Nd_0.25ZrTi_1.75Al_0.25O₇ composition by powder sintering. The samples were then characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy–energy dispersive X-ray spectroscopy (TEM-EDX), and selected area electron diffraction (SAED). The chemical composition of the 100–500 nm zirconolite crystals grown from a glass matrix was determined by TEM-EDX to be Ca_0.83Nd_0.25Zr_0.85Ti_1.95Al_0.11O₇. PXRD and SAED results showed that these two Al–Nd codoped zirconolite phases were crystallized in space group C12/c1. The HRTEM images and SAED results showed that there were heavy stacking faults in the zirconolite crystals grown from the glass matrix. In contrast, far fewer defects were found in the zirconolite crystals prepared by powder sintering. The split-atom model was adopted for the first time to construct the Al–Nd codoped zirconolite structure grown from glass during the Rietveld refinement. The isostructural method assisted by Rietveld refinement was used to resolve the Al–Nd codoped zirconolite structures prepared by different methods. The occupancies of the cation sites were identified, and the distribution behavior of Nd³⁺ was further investigated. The results indicate that the heavy stacking faults may lead to substantial differences in the Al–Nd codoped zirconolite structures prepared by these two fabrication routes.

更新日期：2015-07-23

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