Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Single-crystal X-ray diffraction and temperature dependent (super 57) Fe Moessbauer spectroscopy on the hedenbergite-aegirine (Ca,Na)(Fe (super 2+) ,Fe (super 3+) )Si (sub 2) O (sub 6) solid solution

Guenther J. Redhammer, Georg Amthauer, Georg Roth, Gerold Tippelt and Werner Lottermoser
Single-crystal X-ray diffraction and temperature dependent (super 57) Fe Moessbauer spectroscopy on the hedenbergite-aegirine (Ca,Na)(Fe (super 2+) ,Fe (super 3+) )Si (sub 2) O (sub 6) solid solution
American Mineralogist (August 2006) 91 (8-9): 1271-1292

Abstract

Synthetic samples with different chemical compositions along the hedenbergite-aegirine (CaFe (super 2+) Si (sub 2) O (sub 6) -NaFe (super 3+) Si (sub 2) O (sub 6) ) solid-solution series have been investigated by single-crystal X-ray diffraction and (super 57) Fe Mossbauer spectroscopy. All compounds show C2/c symmetry, both at 298 K and at low temperature (100 K). The structural changes within the hedenbergite-aegirine series are dominated by the M1 site while the M2 site plays a minor role. Replacement of Fe (super 2+) by Fe (super 3+) increases the polyhedral distortion of the M1 site and causes an increased repulsion between neighboring M1 sites. The changes in M1-site geometry also induce distinct alterations within the kinking state of the tetrahedral chains, but the changes in tetrahedral bond lengths and angles are small. In addition to the single-crystal X-ray diffraction experiments, a large number of synthetic samples were investigated by (super 57) Fe Mossbauer spectroscopy at 298 K and, for three selected compositions, between 80 and 700 K. Here, substantial line broadening of the Fe (super 2+) resonance absorption was observed as an aegirine component is substituted. Two different groups of local distortion environments were observed for Fe (super 2+) within the solid-solution series, which change relative proportions and numeric value of the quadrupole splitting as a function of chemistry and temperature. This line broadening cannot be ascribed to discrete next-nearest-neighbor (NNN) configurations of Ca and Na as has been done in the literature. Above approximately 250 K, additional resonance absorption appears in the spectra of samples with aegirine components between 20 and 75 mol%. This absorption gains intensity with increasing temperature, while the (super 57) Fe hyperfine parameters approach values intermediate between Fe (super 2+) and Fe (super 3+) . This effect is ascribed to fast electron delocalization between Fe (super 2+) and Fe (super 3+) at elevated temperature.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 91
Serial Issue: 8-9
Title: Single-crystal X-ray diffraction and temperature dependent (super 57) Fe Moessbauer spectroscopy on the hedenbergite-aegirine (Ca,Na)(Fe (super 2+) ,Fe (super 3+) )Si (sub 2) O (sub 6) solid solution
Affiliation: University Salzburg, Department of Material Science, Salzburg, Austria
Pages: 1271-1292
Published: 200608
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 40
Accession Number: 2006-079761
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
Secondary Affiliation: Rheinisch-Westfaelische Technische Hochschule Aachen, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200645
Close Modal

or Create an Account

Close Modal
Close Modal