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Title: Intervalence charge transfer in aluminum oxide and aluminosilicate minerals at elevated temperatures
Abstract Single-crystal optical spectra of corundum (Al2O3) and the Al2SiO5 polymorphs andalusite, kyanite, and sillimanite, containing both Fe2+-Fe3+ and Fe2+-Ti4+ intervalence charge transfer (IVCT) absorption bands were measured at temperatures up to 1000 °C. Upon heating, thermally equilibrated IVCT bands significantly decreased in intensity and recovered fully on cooling. These trends contrast with the behavior of crystal field bands at temperature for Fe, Cr, and V in corundum, kyanite, and spinel. The effects of cation diffusion and aggregation, as well as the redistribution of band intensity at temperature, are also discussed. The loss of absorption intensity in the visible and near-infrared regions of the spectrum of these phases may point to a more general behavior of IVCT in minerals at temperatures within the Earth with implications for radiative conductivity within the Earth.  more » « less
Award ID(s):
2148727
PAR ID:
10560282
Author(s) / Creator(s):
;
Publisher / Repository:
American Mineralogist
Date Published:
Journal Name:
American Mineralogist
Volume:
109
Issue:
12
ISSN:
0003-004X
Page Range / eLocation ID:
2152 to 2161
Subject(s) / Keyword(s):
Intervalence charge transfer temperature dependence corundum andalusite kyanite sillimanite
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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