Local structure of the metal–oxygen bond in compositionally homogeneous, nanocrystalline zirconia–ceria solid solutions synthesized by a gel-combustion process

Abstract

Compositionally homogeneous ZrO2–CeO2 nanopowders have been characterized by Raman and extended x-ray absorption fine structure (EXAFS) spectroscopies. These techniques revealed a tetragonal-to-cubic phase transition as a function of CeO2 content, as observed in a previous synchrotron x-ray diffraction study. The tetragonal–cubic phase boundary was found to be at (85 ± 5) mol% CeO2. The EXAFS study demonstrated that this transition is related to a tetragonal-to-cubic symmetry change of the Zr–O first neighbour coordination sphere, while the Ce–O coordination sphere preserves its cubic symmetry over the whole composition range.

Tetragonal-cubic phase boundary in nanocrystalline ZrO2–Y2O3 solid solutions synthesized by gel-combustion

“…6 displays this ratio, which exhibits a monotonous decrease with composition and became zero between 10 and 11 mol% Y 2 O 3 . This result indicates that the t /c transition in nanocrystalline ZrO 2 -Y 2 O 3 solid solutions occurs at (10.5 ± 0.5) mol% Y 2 O 3, in good agreement with the value independently determined by the above SXPD analysis following the intensity of the 1 1 2 Bragg peak and with the previous results reported by Yashima [22], a clearly linear behavior is observed over the whole composition range, thus confirming the compositionally homogeneous nature of the solid solutions prepared by the gel-combustion procedure [10][11][12][13][14][23][24][25][26][27][28][29]. The compositional homogeneity of materials synthesized by gel-combustion routes can be explained considering that the system remains homogeneous during the whole process and the final combustion step of the precursor gel proceeds very rapidly, thus preserving the compositional homogeneity in the as-reacted material.…”

Local atomic structure in tetragonal pure ZrO2nanopowders

“…Previous studies of the local atomic order of nanocrystalline ZrO 2 -CeO 2 solid solutions for samples with average crystallite sizes between 8 and 20 nm (Fá bregas et al, 2006) established a sevenfold coordination of Zr atoms over a wide range of compositions, from 15 to 80 mol% CeO 2 . In these investigations, Model 3 was applied and a good agreement between SR-XRD and EXAFS results was obtained.…”

“…Data reduction was performed using the WinXas code (Ressler, 1998) following the procedure described elsewhere (Fá bregas et al, 2006(Fá bregas et al, , 2008. Both pre-and post-edge backgrounds were subtracted from the raw data.…”

Integrated study of experiment and first‐principles computation for the characterization of a corium type ZrO 8 complex in a Zr‐doped fluorite UO 2

“…As far as the authors understand, however, the microstructural analysis of the (U,Zr)O 2 system using Raman spectroscopy has been very rarely carried out. There are previous reports applying Raman spectroscopy to a (Ce,Zr)O 2 , which has the same fluorite structure as (U,Zr)O 2 . Interestingly, it was suggested that ZrO 8 ‐type complex formed at certain Zr doping levels, presumably by incorporation of Zr into the fluorite CeO 2 matrix .…”