Structural studies of new inorganic oxides and polymer electrolytes

Abstract

A knowledge of structure is crucial to the understanding of inorganic solids and polymers. Neutron and X-ray powder diffraction are two powerful complementary techniques which can be used in the structural characterisation of a variety of crystalline materials. Chemical and electrochemical oxygen intercalation techniques involving both aqueous and non-aqueous systems, have been investigated for a number of crystalline inorganic oxides. The pyrochlore structure has been discovered to be a new class of host for the chemical intercalation of oxygett and the interstitial solid solution of Ce₂Zr₂O₇₊x based on this structure-type has been investigated. Intercalation in this system is found to involve an unusual mechanism of oxygen displacement. The structures of other complex metal oxides have also been elucidated using a combination of X-ray and neutron powder diffraction, including those of Li₂9Zr9Nb₃O₄0 and Li₂9Zr9.₆Ta₂.₄O₄0. The doping behaviour of magnesium into the technologically important material lithium niobate has also been studied using these techniques. Polymer electrolytes are a class of ionically conducting solid phases formed by the dissolution of salts in ion co-ordinating macromolecules. The relationship between the crystalline and amorphous phase of the polymer-salt complex PEO₃.LiCF₃SO₃ has been examined by variable-temperature powder X-ray diffraction. This has shed new light on the relationship between the crystalline and amorphous structures of polymer electrolytes. Finally, the crystal structure of the polymer-salt complex PEO₄:RbSCN has been determined.