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Grain‐Boundary Characterization in a Nonstoichiometric Fine‐Grained Magnesium Aluminate Spinel: Effects of Defect Segregation at the Space‐Charge Layers
Author(s) -
Nuns Nicolas,
Béclin Franck,
Crampon Jacques
Publication year - 2009
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02901.x
Subject(s) - grain boundary , spinel , materials science , space charge , mineralogy , grain boundary diffusion coefficient , crystallographic defect , grain size , analytical chemistry (journal) , metallurgy , crystallography , chemistry , microstructure , physics , chromatography , quantum mechanics , electron
The grain‐boundary chemistry of fine‐grained spinel MgO· n Al 2 O 3 (mean grain size below micron) has been investigated by STEM microanalysis. We have quantified the concentration of each element across the grain boundaries. Stoichiometry variations are observed from the grain‐boundary region to the bulk. The Al/Mg ratio increases from 2.1 in the bulk to 2.35 at the grain‐boundary regions. X‐ray quantification allows us to reveal and to characterize the space‐charge layer in the subgrain boundary. The grain‐boundary cores are negatively charged due tovacancies in excess, and in the subgrain‐boundary region, an opposite, positive space‐charge layer is obtained. The point defect composition and the characteristic (sign, space‐charge potential Φ ∞ ) of the space‐charge layer are discussed.