Details

Autor(en) / Beteiligte

• Vannier, R N
• Pernot, E
• Anne, M
• Isnard, O
• Nowogrocki, G
• Mairesse, G

Titel

Bi4V2O11 polymorph crystal structures related to their electrical properties

Ist Teil von

• Solid state ionics, 2003-02, Vol.157 (1-4), p.147-153

Erscheinungsjahr

2003

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Combining X-ray single crystal and neutron powder diffraction data, the crystal structures of the three polymorphs of Bi4VaO11 were refined. These polymorphs can be described from a common orthorhombic mean cell with approximate parameters: am #~ 5.5, bm #~ 5.6 and cm #~ 15.3 A. They are all built upon well-defined Bi2O2+ layers spaced by perovskite-like VO3.5 slabs. A large disorder of the oxygen located in these slabs was observed for the *g phase in which the diffusion is very fast. The decrease in temperature leads to an ordering of the oxygen vacancies in the *b and *a-polymorphs. The oxygen packing in the *b-polymorph remains close to that of a distorted perovskite with a vacancy located on one site. This perovskite lattice is not maintained in the *a-polymorph. The *b to a transition is reconstructive with the formation of typical trigonal bipyramids leading to a 6am superstructure. Because of the high parameter to data ratio, the structure of this *a-polymorph was modelled in the smaller 3am superstructure. This superstructure can be explained by an ordering of some oxygen vacancies along [010]. However, this ordering could be more complex and some disorder may remain in this area, which would explain the low activation energy observed for this *a-polymorph. The specific structural characteristics of the three polymorphs of Bi4V2O11 are correlated with their corresponding conductivity and activation energy.