A high temperature superionic phase of CsSn{sub 2}F{sub 5}

Journal Article · Mon Feb 15 00:00:00 EST 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.11.020· OSTI ID:21372493

Berastegui, P ^[1]; Hull, S ^[2]; Eriksson, S G ^[3]

---

1. Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm (Sweden)
2. The ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)
3. Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden)

The compound CsSn{sub 2}F{sub 5} has been investigated over the temperature range from ambient to 545 K using differential scanning calorimetry, impedance spectroscopy and neutron powder diffraction methods. A first-order phase transition is observed from DSC measurements at 510(2) K, to a phase possessing a high ionic conductivity ({sigma}{approx}2.5x10{sup -2} {Omega}{sup -1} cm{sup -1} at 520 K). The crystal structure of the high temperature superionic phase (labelled {alpha}) has been determined to be tetragonal (space group I4/mmm, a=4.2606(10) A, c=19.739(5) A and Z=2) in which the cations form layers perpendicular to the [001] direction, with a stacking sequence CsSnSnCsSnSn... All the anions are located in two partially occupied sites in the gap between the Cs and Sn layers, whilst the space between the Sn cations is empty, due to the orientation of the lone-pair electrons associated with the Sn{sup 2+}. The structure of {alpha}-CsSn{sub 2}F{sub 5} is discussed in relation to two other layered F{sup -} conducting superionic phases containing Sn{sup 2+} cations, {alpha}-RbSn{sub 2}F{sub 5} and {alpha}-PbSnF{sub 4} and, to facilitate this comparison, an improved structural characterisation of the former is also presented. The wider issue of the role of lone-pair cations such as Sn{sup 2+} in promoting dynamic disorder within an anion substructure is also briefly addressed. - Graphical abstract: CsSn{sub 2}F{sub 5} is shown to undergo a first order phase transition at 510(2) K to a superionic phase in which the specific electronic configuration of the Sn{sup 2+} plays a key role in promoting extensive disorder of the anions.

• OSTI ID: 21372493
• Journal Information: Journal of Solid State Chemistry, Vol. 183, Issue 2; Other Information: DOI: 10.1016/j.jssc.2009.11.020; PII: S0022-4596(09)00549-0; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALORIMETRY
CESIUM COMPOUNDS
ELECTRONIC STRUCTURE
FLUORIDES
FLUORINE IONS
IMPEDANCE
IONIC CONDUCTIVITY
NEUTRON DIFFRACTION
PHASE TRANSFORMATIONS
SPACE GROUPS
SPECTROSCOPY
TEMPERATURE RANGE 0400-1000 K
TIN COMPOUNDS
TIN IONS
ALKALI METAL COMPOUNDS
CHARGED PARTICLES
COHERENT SCATTERING
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
IONS
PHYSICAL PROPERTIES
SCATTERING
SYMMETRY GROUPS
TEMPERATURE RANGE