Other
Scientific paper
Sep 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005gecoa..69.4315j&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 69, Issue 17, p. 4315-4332.
Other
11
Scientific paper
The coordination environment of Fe(II) has been examined in seven anhydrous ferrosilicate glasses at 298 K and 1 bar using 57Fe Mössbauer, Fe K-edge X-ray near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS), UV-Vis-NIR, and magnetic circular dichroism (MCD) spectroscopies. Glasses of the following compositions were synthesized from oxide melts (abbreviation and nonbridging oxygen:tetrahedral cation ratio (NBO/T) in parentheses): Li2FeSi3O8 (LI2: 1.33), Rb2FeSi3O8 (RB2: 1.33), Nal.08Fel.l7Si3.l3O8 (NAl: 1.09), Nal.46Ca0.24Fel.08Si2.97O8 (NC6: 1.38), Nal.09Ca0.51Fe0.72Si3.10O8 (NC2: 1.15), Na0.99Ca0.92Fe0.24 Si3.17O8 (NCl: 1.04), and Na0.29Mg0.53Ca0.52Fe0.56Al0.91Si2.44O8 (BAS: 1.05). Mössbauer, XANES, and EXAFS information suggests that iron is dominantly ferrous in all glasses (<10 atom% Fe(III)) with an average first-neighbor Fe(II) coordination varying from ˜ 4 to 5.2 (±0.2) oxygens. The UV-Vis-NIR spectrum of each sample exhibits intense absorption centered near 8100 9200 cm-1 and weak absorption near 5000 cm-l, which cannot be assigned unambiguously. The MCD spectrum of NC6 glass, which is the first such measurement on a silicate glass, shows three transitions at ˜8500 cm-1, ˜6700 cm-1, and ˜4500 cm-1. The behavior of these MCD bands as a function of temperature (1.6 K to 300 K) and magnetic field strength (1 T to 7 T) indicates that they most likely arise from three distinct Fe(II) sites with different ground states, two of which are 5-coordinated and one of which is 4-coordinated by oxygens. The combined results suggest that Fe(II) predominantly occupies 5- and 4-coordinated sites in each glass, with the ratios differing for the different compositions. Small amounts of 6-coordinated Fe(II) are possible as well, but primarily in the more basic glass compositions such as BAS. The substitution of Li(I) for Rb(I) in the M2FeSi3O8 base glass composition causes a weakening of the average Fe(II)-O bond, as indicated by the longer Fe(II)-O distance in the latter. The basalt composition glass was found to have the largest Fe(II) sites relative to those in the other glasses in this study. A bond valence model that helps predict the coordination number of Fe(II) in silicate glasses is proposed. The structural information extrapolated to Fe(II)-bearing melts is parameterized using bond valence theory, which helps to rationalize the melt-crystal partitioning behavior of ferrous iron in natural and synthetic melt-crystal systems.
Brown Gordon E.
Farges François
Jackson William E.
Mabrouk Patricia A.
Rossano Stephanie
No associations
LandOfFree
Multi-spectroscopic study of Fe(II) in silicate glasses: Implications for the coordination environment of Fe(II) in silicate melts does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Multi-spectroscopic study of Fe(II) in silicate glasses: Implications for the coordination environment of Fe(II) in silicate melts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-spectroscopic study of Fe(II) in silicate glasses: Implications for the coordination environment of Fe(II) in silicate melts will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1286241