Structural studies of a ZrO2–CeO2 doped system

• Published in: Journal of the European Ceramic Society Vol. 23; no. 2; pp. 273 - 282
• Main Authors: Mastelaro, Valmor R, Briois, Valérie, de Souza, Dulcina P.F, Silva, Carlos L
• Format: Journal Article
• Language: English
• Published: 01.02.2003
• ISSN: 0955-2219
• DOI: 10.1016/S0955-2219(02)00188-7

The local structure around Zr, Ce and dopant atoms (Fe and Ni) in the ZrO2-CeO2 system was investigated by X-ray absorption spectroscopy to better understand the tetragonal phase stabilisation process of zirconia. The first coordination shell around Zr atoms is not sensitive to the introduction of dopants or to an increase in ceria content (from 12 to 20 mol%). Ce ions maintain eight-fold coordination as in CeO2 but with an altered bond distance. Vacancies resulting from reduction of Ce atoms can be discarded because XANES spectra show that Ce ions are preferentially in a tetravalent state. XANES and EXAFS experiments at the Fe K-edge show that the local order around Fe is different from that of the Fe2O3 oxide. Ab initio EXAFS calculations show that iron atoms form a solid solution with tetragonal ZrO2. The EXAFS simulation of the first coordination shell around iron shows that the substitution of zirconium atoms by iron atoms generates oxygen vacancies in the tetragonal network. This is a driven force for the tetragonal phase stabilisation process. For Ni doped samples, EXAFS results show that Ni-O mean bond length is similar to the distance found in the NiO compound. No evidence of similar solid solution formation for Ni-doped systems emerged from the EXAFS analysis. 29 refs.