Controllable sites and high-capacity immobilization of uranium in Nd(2)Zr(2)O(7) pyrochlore.
Controllable sites and high-capacity immobilization of uranium in Nd(2)Zr(2)O(7) pyrochlore.
复制标题
Nd2Zr2O7 烧绿石中铀的可控位点和高容量固定
DOI：
10.1107/s1600577521012558
复制
发表时间：
2022-01-01
影响因子：
2.5
通讯作者：
Wang JQ
中科院分区：
文献类型：
--
作者：
Sun J;Zhou J;Hu Z;Chan TS;Liu R;Yu H;Zhang L;Wang JQ
首次系统研究了熔盐法合成的掺U Nd 2 Zr 2 O 7用于潜在的锕系元素固定。作为潜在的核废料基质，两个系列的掺铀Nd 2 Zr 2 O 7纳米粒子成功地使用优化的熔盐法在空气气氛中合成。结合X射线衍射、拉曼和X射线吸收精细结构（XAFS）谱研究表明，铀离子可以精确地取代Nd位形成Nd 2-xUxZr 2 O 7 +δ（0 ≤ x ≤ 0.2）体系，取代Zr位形成Nd 2 Zr 2-yUyO 7 +δ（0 ≤ y ≤ 0.4）体系，没有任何杂质相。随着U浓度的增加，有一个从烧绿石（Fd 3 m）到缺陷萤石（Fm 3 m）结构的相变在这两个系列的U掺杂的Nd 2 Zr 2 O 7。XAFS分析表明，铀在所有样品中均以高价U ~（6+）的形式存在。为了平衡用U6+取代Nd 3+或Zr 4+所产生的额外电荷，引入了额外的氧，并伴有较大的结构扭曲;然而，高U负载量（20mol%）的Nd2Zr1.6U0.4O7+δ样品仍然保持着规则的萤石结构，表明Nd 2 Zr 2 O 7主体对铀具有良好的溶解性。 据我们所知，这项研究是第一个系统的研究，通过熔盐法合成的U-掺入Nd 2 Zr 2 O 7，并提供了令人信服的证据，准确地固定在特定位置的U的可行性。
The first systematic study on U-incorporated Nd2Zr2O7 synthesized via a molten salt method for potential actinide immobilization is presented. As potential nuclear waste host matrices, two series of uranium-doped Nd2Zr2O7 nanoparticles were successfully synthesized using an optimized molten salt method in an air atmosphere. Our combined X-ray diffraction, Raman and X-ray absorption fine-structure (XAFS) spectroscopy studies reveal that uranium ions can precisely substitute the Nd site to form an Nd2–x U x Zr2O7+δ (0 ≤ x ≤ 0.2) system and the Zr site to form an Nd2Zr2–y U y O7+δ (0 ≤ y ≤ 0.4) system without any impurity phase. With increasing U concentration, there is a phase transition from pyrochlore (Fd 3 m) to defect fluorite (Fm 3 m) structures in both series of U-doped Nd2Zr2O7. The XAFS analysis indicates that uranium exists in the form of high-valent U6+ in all samples. To balance the extra charge for substituting Nd3+ or Zr4+ by U6+, additional oxygen is introduced accompanied by a large structural distortion; however, the Nd2Zr1.6U0.4O7+δ sample with high U loading (20 mol%) still maintains a regular fluorite structure, indicating the good solubility of the Nd2Zr2O7 host for uranium. This study is, to the best of our knowledge, the first systematic study on U-incorporated Nd2Zr2O7 synthesized via the molten salt method and provides convincing evidence for the feasibility of accurately immobilizing U at specific sites.