Controllable sites and high-capacity immobilization of uranium in Nd2Zr2O7 pyrochlore

Journal of Synchrotron Radiation

Linjuan Zhang¹  Renduo Liu¹  Jing Zhou¹  Jian Sun¹  Jian-Qiang Wang¹  Haisheng Yu¹  Zhiwei Hu²  Ting-Shan Chan³ 

[1] Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, People's Republic of China;Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany;National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan;

关键词: molten salt method;    actinide immobilization;    nd2zr2o7;    x-ray absorption spectroscopy;   

DOI  :  10.1107/S1600577521012558

来源: DOAJ

【 摘 要 】

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–xUxZr2O7+δ (0 ≤ x ≤ 0.2) system and the Zr site to form an Nd2Zr2–yUyO7+δ (0 ≤ y ≤ 0.4) system without any impurity phase. With increasing U concentration, there is a phase transition from pyrochlore (Fd3m) to defect fluorite (Fm3m) 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.

【 授权许可】

Unknown