Electrical conductivity of antimony oxofluoride Sb 3 O 2 F 5
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ICAL PROPERTIES OF CRYSTALS
Electrical Conductivity of Antimony Oxofluoride Sb3O2F5 N. I. Sorokin and B. P. Sobolev Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 119333 Russia email: [email protected] Received June 20, 2012
Abstract—The conductivity of antimony oxofluoride Sb3O2F5 is investigated by the complex impedance method in the temperature range of 400–505 K. Sb3O2F5 powder has been prepared by solidphase synthesis in nickel ampoules at 473 K for 5 h in an argon atmosphere. The Sb3O2F5 conductivity has an ionic character. The ionic conductivity is found to be 5 × 10–5 S/cm (at 505 K), with an ioncarrier migration energy of 0.82 eV. DOI: 10.1134/S1063774513040184
INTRODUCTION The electrical properties of oxofluorides are of great interest because F– and O2– ions are simulta neously present in their composition. Completely solidstate sensors of double purpose (fluorine and oxygen) can be developed on the basis of these materi als if the latter have high anionic conductivity. A pro gram of searching for promising solid electrolytes in different classes of oxofluoride materials [1–3] has been performed at the Institute of Crystallography of the Russian Academy of Sciences (IC RAS). Within this program it was found that Bi oxofluorides have good electrolytic properties. Thus, it is of interest to study the electrical properties of Sb oxofluorides, because Sb and Bi belong to the fifth main subgroup of the periodic system and their ions have high electronic polarizability. According to [4], the high electronic polarizability of cations is one of the criteria of fast anionic transport in solids. A comparison between the phase formation in the SbF3–Sb2O3 system [5] and that in the BiF3–Bi2O3 system [6] shows that there is no analogy between them. Bi oxofluorides have a tendency toward the sta tistical distribution of fluorine and oxygen ions, which results in wide ranges of existence of solid solutions based on BiO0.5F2 with a structure of fluorite type (CaF2) and BiOyF3 – 2y with a structure of tysonite type (LaF3) in the BiF3–Bi2O3 system. Solid solutions are not found in the SbF3–Sb2O3 system; it was shown in [5] that the binary compound Sb3O2F5 (28.6 mol % Sb2O3) is formed in it. It melts with decomposition and can be obtained by solid phase synthesis from SbF3 and Sb2O3 [5] via the inter action of SbF3 with H2O vapor (pyrohydrolysis) [5], or by means of hydrolysis from an SbF3 aqueous solution in the presence of CH3COOH [7]. The structure of Sb3O2F5 crystals was studied in [7]. The electrical properties of Sb3O2F5 crystals are unknown to the best of our knowledge.
This work continues a series of studies of oxofluo rides performed at the IC RAS and is devoted to the conductivity of antimony oxofluoride Sb3O2F5. EXPERIMENTAL CONDITIONS AND DISCUSSION OF RESULTS The object of study was a finegrained powder of Sb3O2F5 supplied by F.V. Kalinchenko, who obtained this compound by solidphase synthesis at 473 K for 5 h in an atmosphere of spectrally pu
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