THE CRYSTAL-CHEMISTRY OF FERRIC IRON IN FE0.05MG0.95SIO3 PEROVSKITE AS DETERMINED BY MOSSBAUER-SPECTROSCOPY IN THE TEMPERATURE-RANGE 80-293K

Authors
Citation
Ca. Mccammon, THE CRYSTAL-CHEMISTRY OF FERRIC IRON IN FE0.05MG0.95SIO3 PEROVSKITE AS DETERMINED BY MOSSBAUER-SPECTROSCOPY IN THE TEMPERATURE-RANGE 80-293K, Physics and chemistry of minerals, 25(4), 1998, pp. 292-300
Citations number
34
Categorie Soggetti
Mineralogy,"Material Science
ISSN journal
03421791
Volume
25
Issue
4
Year of publication
1998
Pages
292 - 300
Database
ISI
SICI code
0342-1791(1998)25:4<292:TCOFII>2.0.ZU;2-S
Abstract
Mossbauer spectra were recorded at multiple temperatures between 80 an d 293 K to study the nature of Fe3+ in Fe0.05Mg0.95SiO3 perovskite tha t had been synthesised in a multianvil press at 1650 degrees C and 25 GPa at its mimimum f(O2) stability limit. The Mossbauer data were fitt ed to a model with quadrupole splitting distributions (Fe2+) and Loren tzian lineshapes (Fe3+ and Fen+). The centre shift data were fitted to a Debye model with the following results: Theta(M) (Fe2+)=365+/-52 K and Theta(M) (Fe3+)=476+/-96 K. Hyperfine parameter data for Fe3+ sugg est occupation of the octahedral site only. The average valence seen b y the Mossbauer effect in rapid electron exchange that occurs between Fe2+ and Fe3+ is calculated from the hyperfine parameters to be 2.50+/ -0.07. Correction of area fractions for site-dependent recoil-free fra ctions gives a value for Fe3+/Sigma Fe of 9.4+/-1.4%, which is indepen dent of temperature. A perovskite phase of similar composition synthes ised in the multianvil press at higher oxygen fugacity gives a value f or Fe3+/Sigma Fe of 16+/-3%, where Fe3+ appears to occupy both sites i n the perovskite structure.