X-ray absorption spectroscopy of doped ZrO2 systems
Amlan Chakrabarti2012, Journal of Applied Physics
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Abstract
ZrO 2 samples with 11% Nd and La doping and with 7, 9, 11, and 13% Gd doping have been prepared by co-precipitation route followed by sintering at 700 C and 1100 C, for potential application as high conductivity electrolytes in solid oxide fuel cells. The samples have been characterized by x-ray diffraction with laboratory x-ray source of Cu K a radiation and extended x-ray absorption fine structure (EXAFS) spectroscopy measurement at Zr K edge with synchrotron radiation. The XRD spectra have been analyzed to determine the structure of the samples and the EXAFS data have been analyzed to find out relevant local structure parameters of the Zr-O and Zr-Zr shells, viz., bond distances, co-ordinations, and disorder parameters. The effect of change in ionic radius as well as concentration of the dopants on the above parameters has been thoroughly studied. The experimental results, in some cases, have also been corroborated by first principle calculations of the energetics of the systems. V C 2012 American Institute of Physics.
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ZrO 2 samples with 11% Nd and La doping and with 7, 9, 11, and 13% Gd doping have been prepared by co-precipitation route followed by sintering at 700 C and 1100 C, for potential application as high conductivity electrolytes in solid oxide fuel cells. The samples have been characterized by x-ray diffraction with laboratory x-ray source of Cu K a radiation and extended x-ray absorption fine structure (EXAFS) spectroscopy measurement at Zr K edge with synchrotron radiation. The XRD spectra have been analyzed to determine the structure of the samples and the EXAFS data have been analyzed to find out relevant local structure parameters of the Zr-O and Zr-Zr shells, viz., bond distances, co-ordinations, and disorder parameters. The effect of change in ionic radius as well as concentration of the dopants on the above parameters has been thoroughly studied. The experimental results, in some cases, have also been corroborated by first principle calculations of the energetics of the systems. V C 2012 American Institute of Physics.
Structural studies of a ZrO 2–CeO 2 doped system
Journal of The European Ceramic Society, 2003
The local structure around Zr, Ce and dopant atoms (Fe and Ni) in the ZrO 2 -CeO 2 system investigated by X-ray absorption spectroscopy (XAS) is reported to better understand the tetragonal phase stabilization process of zirconia. The first coordination shell around Zr atoms is not sensitive to the introduction of dopants or to an increase in the ceria content (from 12 to 20 mol%). Ce ions maintain the eight-fold coordination as in CeO 2 , but with an altered bond distance. The formation of vacancies resulting from reduction of Ce atoms can be discarded, because XANES spectra clearly show that Ce ions are preferentially in a tetravalent state. XANES and EXAFS experiments at the Fe K-edge evidence that the local order around Fe is quite different from that of the Fe 2 O 3 oxide. On the one hand, ab initio EXAFS calculations show that iron atoms form a solid solution with tetragonal ZrO 2 . The EXAFS simulation of the first coordination shell around iron evidences that the substitution of zirconium atoms by iron ones generates oxygen vacancies into the tetragonal network. This is a driven force for the tetragonal phase stabilization process. For Ni doped samples, EXAFS results show that Ni-O mean bond length is similar to the distance found in the oxide material, i.e., NiO compound. Besides this result, no evidence of similar solid solution formation for Ni-doped systems has emerged from the EXAFS analysis . #
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