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Mössbauer effect study of anapaite, Ca2Fe2+(PO4)2∙4H2O, and of its oxidation products

Sigrid Eeckhout, Eddy De Grave UGent, Renaud Vochten and NM Blaton (1999) PHYSICS AND CHEMISTRY OF MINERALS. 26(6). p.506-512
abstract
Mossbauer spectra (MS) of anapaite (Ca-2 Fe2+ (PO4)(2) . 4H(2)O) and of a sample after being immersed in a 4% H2O2 solution at room temperature (RT) over 12 days (hereafter an4ox) were collected at temperatures in the range 4.2 to 420 K and 11 to 300 K respectively. All MS consist of symmetrical doublets. hence magnetic ordering was not observed. The Fe2+ centre shifts of temperature dependencies of the Fe2+ centre shifts of anapaite and an4ox were analysed with the Debye model for the lattice vibrations. The characteristic Mossbauer temperatures were found as 370 K +/- 25 K and 340 K +/- 25 It. and the intrinsic isomer shifts as 1.427 +/- 0.005 mm/s and 1.418 +/- 0.005 mm/s respectively. From the external-field (60 kOe) MS recorded at 4.2 and 189 K for the non-treated sample, the principal component V-zz of the electric field gradient (EFG) is determined to be positive and the asymmetry parameter eta approximate to 0.2 and 0.4 respectively. The temperature variations of the quadrupole splittings, Delta E-Q(T), cannot be interpreted on the basis of the thermal population of the D-5 electronic levels resulting from the tetragonal compression of the O-6 co-ordination. The low-temperature linear behaviour of Delta E-Q(T) is attributed to a strong orbit-lattice coupling. A field of 60 kOe applied to anapaite at 4.2 K produces magnetic hyperfine splitting with effective hyperfine fields of -136. -254 and -171 kOe along the principal axes Ox, Oy and Oz of the EFG tensor respectively. Additional oxidation treatments in solutions with various H2O2 concentrations up to 20% and subsequent Mossbauer experiments at room temperature, have revealed that the anapaite structure is not sensitive to oxidation since eventually only a small amount of Fe2+ (similar to 6.5%) is converted into Fe3+.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
Mossbauer spectroscopy, anapaite, oxidation, QUADRUPOLE
journal title
PHYSICS AND CHEMISTRY OF MINERALS
Phys. Chem. Miner.
volume
26
issue
6
pages
506 - 512
Web of Science type
Article
Web of Science id
000081850100011
ISSN
0342-1791
DOI
10.1007/s002690050213
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
175310
handle
http://hdl.handle.net/1854/LU-175310
date created
2004-01-14 13:40:00
date last changed
2016-12-19 15:38:07
@article{175310,
  abstract     = {Mossbauer spectra (MS) of anapaite (Ca-2 Fe2+ (PO4)(2) . 4H(2)O) and of a sample after being immersed in a 4\% H2O2 solution at room temperature (RT) over 12 days (hereafter an4ox) were collected at temperatures in the range 4.2 to 420 K and 11 to 300 K respectively. All MS consist of symmetrical doublets. hence magnetic ordering was not observed. The Fe2+ centre shifts of temperature dependencies of the Fe2+ centre shifts of anapaite and an4ox were analysed with the Debye model for the lattice vibrations. The characteristic Mossbauer temperatures were found as 370 K +/- 25 K and 340 K +/- 25 It. and the intrinsic isomer shifts as 1.427 +/- 0.005 mm/s and 1.418 +/- 0.005 mm/s respectively. From the external-field (60 kOe) MS recorded at 4.2 and 189 K for the non-treated sample, the principal component V-zz of the electric field gradient (EFG) is determined to be positive and the asymmetry parameter eta approximate to 0.2 and 0.4 respectively. The temperature variations of the quadrupole splittings, Delta E-Q(T), cannot be interpreted on the basis of the thermal population of the D-5 electronic levels resulting from the tetragonal compression of the O-6 co-ordination. The low-temperature linear behaviour of Delta E-Q(T) is attributed to a strong orbit-lattice coupling. A field of 60 kOe applied to anapaite at 4.2 K produces magnetic hyperfine splitting with effective hyperfine fields of -136. -254 and -171 kOe along the principal axes Ox, Oy and Oz of the EFG tensor respectively. Additional oxidation treatments in solutions with various H2O2 concentrations up to 20\% and subsequent Mossbauer experiments at room temperature, have revealed that the anapaite structure is not sensitive to oxidation since eventually only a small amount of Fe2+ (similar to 6.5\%) is converted into Fe3+.},
  author       = {Eeckhout, Sigrid and De Grave, Eddy and Vochten, Renaud and Blaton, NM},
  issn         = {0342-1791},
  journal      = {PHYSICS AND CHEMISTRY OF MINERALS},
  keyword      = {Mossbauer spectroscopy,anapaite,oxidation,QUADRUPOLE},
  language     = {eng},
  number       = {6},
  pages        = {506--512},
  title        = {M{\"o}ssbauer effect study of anapaite, Ca2Fe2+(PO4)2\unmatched{2219}4H2O, and of its oxidation products},
  url          = {http://dx.doi.org/10.1007/s002690050213},
  volume       = {26},
  year         = {1999},
}

Chicago
Eeckhout, Sigrid G, Eddy De Grave, Renaud Vochten, and NM Blaton. 1999. “Mössbauer Effect Study of Anapaite, Ca2Fe2+(PO4)2∙4H2O, and of Its Oxidation Products.” Physics and Chemistry of Minerals 26 (6): 506–512.
APA
Eeckhout, S. G., De Grave, E., Vochten, R., & Blaton, N. (1999). Mössbauer effect study of anapaite, Ca2Fe2+(PO4)2∙4H2O, and of its oxidation products. PHYSICS AND CHEMISTRY OF MINERALS, 26(6), 506–512.
Vancouver
1.
Eeckhout SG, De Grave E, Vochten R, Blaton N. Mössbauer effect study of anapaite, Ca2Fe2+(PO4)2∙4H2O, and of its oxidation products. PHYSICS AND CHEMISTRY OF MINERALS. 1999;26(6):506–12.
MLA
Eeckhout, Sigrid G, Eddy De Grave, Renaud Vochten, et al. “Mössbauer Effect Study of Anapaite, Ca2Fe2+(PO4)2∙4H2O, and of Its Oxidation Products.” PHYSICS AND CHEMISTRY OF MINERALS 26.6 (1999): 506–512. Print.