Observing Local Oxygen Interstitial Diffusion in Donor-Doped Ceria by 17O NMR Relaxometry

详细信息    查看全文

• 作者：Ralf Heinzmann ; Ibrahim Issac ; Jens-Peter Eufinger ; Gregor Ulbrich ; Martin Lerch ; Jürgen Janek ; Sylvio Indris
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：April 28, 2016
• 年：2016
• 卷：120
• 期：16
• 页码：8568-8577
• 全文大小：526K
• 年卷期：0
• ISSN：1932-7455

文摘

The local structure and oxygen ion dynamics in pure CeO₂ and CeO₂ doped with Ta and Gd is studied by ¹⁷O nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy, and conductivity measurements. ¹⁷O magic-angle spinning nuclear magnetic resonance spectra of CeO₂ doped with Ta show two oxygen environments. A major peak at 876 ppm represents the oxygen ions on the regular crystal lattice site with four Ce⁴⁺ neighbors. A second small peak at 751 ppm (1–2% area fraction) represents point defects that can be ascribed to interstitial oxygen ions. The concentration of these point defects increases with the dopant concentration. Oxygen ion dynamics was studied by variable-temperature spin–lattice relaxation time measurements on pure and Ta-doped CeO₂ powders. The obtained results reveal a fast local jump process in Ta-doped CeO₂ with a jump rate of about 2.5·10⁸ s^–1 at 350 K. This local hopping process is assigned to interstitial oxygen ions trapped by tantalum dopand ions.