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.
electrical-conductivity
disorder
Superionic conduction
ionic-conductivity
strontium bromide
Phase transitions
neutron powder diffraction
barium-chloride
Neutron diffraction
alkaline-earth
thermal-expansion
lead ii fluoride
Alkaline-earth halides
Fluorite structure
defect structure
anion
Author
S. Hull
STFC Rutherford Appleton Laboratory
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 2925-2935Subject Categories (SSIF 2011)
Chemical Sciences
DOI
10.1016/j.jssc.2011.09.004