Temperature-induced iron oxidation in bafertisite Ba2Fe 42+ Ti2(Si2O7)2O2(OH)2F2: X-ray diffraction and Mössbauer spectroscopy study

Elena S. Zhitova, Андрей Золотарев, Sergey V. Krivovichev, Alexey G. Goncharov, Faina A. Gabdrakhmanova, Nikolay V. Vladykin, Maria G. Krzhizhanovskaya, Vladimir V. Shilovskikh, Natalia S. Vlasenko, Anatoly A. Zolotarev

Research output

2 Citations (Scopus)

Abstract

The high-temperature behavior of bafertisite was studied by combination of techniques in order to characterize the temperature-induced iron oxidation associated with deprotonation of an octahedral layer. The chemical formula of bafertisite from Darai-Pioz alkaline complex (Tajikistan) determined by electron-microprobe analyzes and Mössbauer spectroscopy is Ba 2.11(Fe2.702+Fe0.173+Mn 1.09Zr 0.04Na 0.03) (Ti 1.96Nb 0.07)(Si 2O7)2O2(OH 1.29 O 0.65F0.06)F2. In situ high-temperature powder X-ray diffraction revealed abrupt shift of reflections to the high-angle region and reduction of their intensity at T > 525 C. The Mössbauer spectroscopy studies indicated that the crystal structure of bafertisite contains Fe in octahedral sites as predominantly ferric ions with Fe 3+/ ΣFe = 0.06, whereas bafertisite annealed at T = 600 C has Fe in the same position with Fe 3+/ ΣFe up to 0.39. The differential scanning calorimetry and thermogravimetric analyzes reveal the occurrence of a broad exothermic effect at T ∼ 537 C associated with the mass loss corresponding to deprotonation. Since in the studied sample of bafertisite, Fe 2+apfu strongly prevails over OH apfu, the stoichiometric (charged-balanced) high-temperature oxidized modification cannot be obtained. In the paper, the high-temperature behavior of bafertisite is discussed and compared to that of astrophyllite.

Original languageEnglish
Article number96
JournalHyperfine Interactions
Volume238
Issue number1
DOIs
Publication statusPublished - 1 Nov 2017

    Fingerprint

Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Nuclear and High Energy Physics
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

Cite this