High temperature crystal structures and superionic properties of SrCl2, SrBr2, BaCl2 and BaBr2
Artikel i vetenskaplig tidskrift, 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.

Phase transitions

barium-chloride

defect structure

Superionic conduction

lead ii fluoride

disorder

Neutron diffraction

strontium bromide

thermal-expansion

Alkaline-earth halides

neutron powder diffraction

alkaline-earth

anion

Fluorite structure

ionic-conductivity

electrical-conductivity

Författare

S. Hull

ISIS Facility

Stefan Norberg

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Istaq Ahmed

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Sten Eriksson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

C. E. Mohn

Universitetet i Oslo

Journal of Solid State Chemistry

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

Vol. 184 2925-2935

Ämneskategorier

Kemi

DOI

10.1016/j.jssc.2011.09.004