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Role of Structural Fe(III) and Iron Oxide Nanophases in Mullite Coloration
Author(s) -
Djemai Amédée,
Calas Georges,
Muller Jean Pierre
Publication year - 2001
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.1151-2916.2001.tb00887.x
Subject(s) - mullite , iron oxide , materials science , ferric , ion , diffuse reflection , electron paramagnetic resonance , oxide , diffuse reflectance infrared fourier transform , analytical chemistry (journal) , absorption spectroscopy , inorganic chemistry , chemistry , ceramic , nuclear magnetic resonance , photocatalysis , metallurgy , optics , biochemistry , physics , organic chemistry , chromatography , catalysis
Six mullite samples, derived from heat‐treated natural kaolinites with various iron content, were investigated and compared to synthetic monophasic mullite. They were analyzed by X‐ray diffraction, diffuse reflectance spectroscopy, and electron paramagnetic resonance. To quantify mullite coloration, the CIE colorimetric system was used. In contrast to synthetic mullite, samples showed charge transfer bands involving O 2− and Fe 3+ ions as well as ferric crystal‐field transitions due to Fe 3+ ions in iron oxide nanoparticles. Absorption edges showed red shifts. The resulting yellowness, saturation of which increased with the content of iron oxide nanoparticles, is direct evidence for the coloring effect of Fe 3+ ions.