High temperature crystal structures and superionic properties of SrCl2, SrBr2, BaCl2 and BaBr2
Journal article, 2011

The structural properties of the binary alkaline-earth halides SrCl(2), SrBr(2), BaCl(2) and BaBr(2) have been investigated from ambient temperature up to close to their melting points, using the neutron powder diffraction technique. Fluorite-structured SrCl(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(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(2), BaCl(2) and BaBr(2) both adopt the cotunnite crystal structure under ambient conditions. BaCl(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.

defect structure

alkaline-earth

lead ii fluoride

ionic-conductivity

anion

Superionic conduction

disorder

Fluorite structure

barium-chloride

neutron powder diffraction

electrical-conductivity

thermal-expansion

Alkaline-earth halides

Neutron diffraction

Phase transitions

strontium bromide

Author

S. Hull

ISIS Facility

Stefan Norberg

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Istaq Ahmed

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

Sten Eriksson

Chalmers, Chemical and Biological Engineering, Environmental Inorganic Chemistry

C. E. Mohn

University of Oslo

Journal of Solid State Chemistry

0022-4596 (ISSN) 1095-726X (eISSN)

Vol. 184 11 2925-2935

Subject Categories

Chemical Sciences

DOI

10.1016/j.jssc.2011.09.004

More information

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5/8/2018 6