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 2925-2935Subject Categories
Chemical Sciences
DOI
10.1016/j.jssc.2011.09.004