High temperature crystal structures and superionic properties of SrCl{sub 2}, SrBr{sub 2}, BaCl{sub 2} and BaBr{sub 2}

Journal Article · Tue Nov 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.09.004· OSTI ID:21580058

Hull, Stephen ^[1]; Norberg, Stefan T ^[1]; Ahmed, Istaq; Eriksson, Sten G ^[2]; Mohn, Chris E ^[3]

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1. The ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)
2. Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden)
3. Department of Chemistry and Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway)

The structural properties of the binary alkaline-earth halides SrCl{sub 2}, SrBr{sub 2}, BaCl{sub 2} and BaBr{sub 2} have been investigated from ambient temperature up to close to their melting points, using the neutron powder diffraction technique. Fluorite-structured SrCl{sub 2} undergoes a gradual transition to a superionic phase at 900-1100 K, characterised by an increasing concentration of anion Frenkel defects. At a temperature of 920(3) K, the tetragonal phase of SrBr{sub 2} undergoes a first-order transition to a cubic fluorite phase. This high temperature phase shows the presence of extensive disorder within the anion sublattice, which differs from that found in superionic SrCl{sub 2}. BaCl{sub 2} and BaBr{sub 2} both adopt the cotunnite crystal structure under ambient conditions. BaCl{sub 2} undergoes a first-order structural transition at 917(5) K to a disordered fluorite-structured phase. The relationship between the (disordered) crystal structures and the ionic conductivity behaviour is discussed and the influence of the size of the mobile anion on the superionic behaviour is explored. - Graphical abstract: Anomalous behaviour of the lattice expansion of SrCl{sub 2} at temperatures of {approx}1000 K is associated with the gradual transition to a superionic phase, whilst SrBr{sub 2} undergoes a first-order structural transition ({beta}{yields}{alpha}) to a fluorite-structured superionic phase at 920(3) K. Highlights: > Anomalous behaviour of the lattice expansion of SrCl{sub 2} occurs at temperatures {approx}1000 K. > Crystal structure of {beta}-SrBr{sub 2} is described in detail. > On heating, SrBr{sub 2} and BaCl{sub 2} transform to a fluorite-structured superionic phase. > Temperature dependence of the BaCl{sub 2} and BaBr{sub 2} structures is presented. > Nature of the superionic phases within the alkaline-earth halides is discussed.

• OSTI ID: 21580058
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 11; Other Information: DOI: 10.1016/j.jssc.2011.09.004; PII: S0022-4596(11)00486-5; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMBIENT TEMPERATURE
ANIONS
BARIUM BROMIDES
BARIUM CHLORIDES
FLUORITE
FRENKEL DEFECTS
IONIC CONDUCTIVITY
MELTING POINTS
NEUTRON DIFFRACTION
PHASE TRANSFORMATIONS
STRONTIUM BROMIDES
STRONTIUM CHLORIDES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BROMIDES
BROMINE COMPOUNDS
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
COHERENT SCATTERING
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HALIDE MINERALS
HALIDES
HALOGEN COMPOUNDS
IONS
MINERALS
PHYSICAL PROPERTIES
POINT DEFECTS
SCATTERING
STRONTIUM COMPOUNDS
TEMPERATURE RANGE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VACANCIES