SHORT RANGE ORDER IN SUPERIONIC CONDUCTORS

J. Boilot , A. Kahn , J. Thery , G. Collin , R. Comes

Superionic conductors have potential application in new types of batteries, fuel cells and sensors. Our purpose is to present the results obtained by both classical X-ray diffraction and X-ray diffuse scattering techniques on some of them and to show what kind of information could be expected in relation with properties : - X-ray diffraction is a very powerful method for the study of ion repartition on the various available sites of crystal lattice and of changes of this repartition with respect to temperature, preparation conditions.. . - X-ray diffuse scattering provides insight on the real local organization of ions at a scale of a few unit cells and in principle the most direct information about ion-ion interactions. All superionic conductors exhibit extended defects structure which are responsible of their high ionic conductivity. The most important of them is beta alumina with very attractive properties. In this case, the disorder is essentially two dimensional. Structural determinations are deduced from Bragg diffraction show a repartition of conduction ion on three kinds of sites B-R, m-O, aB-R, with important differences between Na+, K+, Tl+ and Ag+. and also the occurrence of Frenkel defects, as seen by Roth and interstitial oxygen providing the compensation mechanism for non-stoichiometry. Diffuse X-ray scattering indicates several types of local orders : one for Na+ ions one for Ag+ ions which, at high temperature, are in a two dimensional quasi-liquid state and another for K+ and Tl+ ions closely related to the local arrangement in low temperature silver beta alumina.

Domaines: Articles anciens

J. Boilot, A. Kahn, J. Thery, G. Collin, R. Comes. SHORT RANGE ORDER IN SUPERIONIC CONDUCTORS. Journal de Physique Colloques, 1977, 38 (C7), pp.C7-145-C7-150. ⟨10.1051/jphyscol:1977727⟩. ⟨jpa-00217228⟩