ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
X-ray absorption near-edge structure (XANES) depends on stereochemical features of coordination polyhedra around probe atoms. K-edge XANES of Y and Zr segregated in alumina grain boundaries has been obtained and analyzed using metallic Y and Zr, Y2O3, YAG, and monoclinic ZrO2 as standards. Grain-boundary-segregated Y and Zr show a positive chemical shift, and the magnitude of the shift, as compared with that of Y2O3 and ZrO2, respectively, is different for Y and Zr, indicating that, relative to Y2O3 and ZrO2, charge transfers for the grain-boundary-segregated Y and Zr are different. This result is also supported by the strength of the threshold resonance. A pre-edge shoulder is seen in K-edge XANES for grain-boundary-segregated Y and Zr but not for Y2O3 and ZrO2. This shoulder is attributed to the 1s→ 4d transition, which is normally forbidden, but can occur because of d–p mixing, which is favored by a tetrahedral coordination configuration. These results suggest that some of the grain-boundary-segregated Y and Zr have coordination configurations with a well-defined tetrahedral symmetry. The XANES results are compared with those obtained from EXAFS. Implications of these results for understanding of the enhanced creep resistance in alumina are also discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.2002.tb00486.x
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