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

S. Hull ; Stefan T. Norberg (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Istaq Ahmed (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Sten G. Eriksson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; C. E. Mohn
Journal of Solid State Chemistry (0022-4596). Vol. 184 (2011), 11, p. 2925-2935.
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: Superionic conduction, Alkaline-earth halides, Neutron diffraction, Phase transitions, Fluorite structure, neutron powder diffraction, lead ii fluoride, ionic-conductivity, strontium bromide, barium-chloride, alkaline-earth, electrical-conductivity, thermal-expansion, defect structure, anion, disorder



Denna post skapades 2011-12-01. Senast ändrad 2016-07-06.
CPL Pubid: 149348

 

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Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Kemi

Chalmers infrastruktur