Synthesis and characterisation of d-Bi2O3 related materials stabilised by substitutions of Ca, Ga, Nb and Re.

[摘要] The work reported in this thesis is based around substitutions into bismuth oxide, which has proven to be highly adaptable chemically as it can accommodate a wide variety of substituents. The synthesis and characterisation of stabilised \(\delta\)-Bi\(_2\)O\(_3\) related materials containing small amounts of Ca, Ga, Nb and Re are described. A body of work is presented exploring the structural and physical properties of such materials, characterised by neutron powder diffraction, X-ray powder diffraction, electron diffraction, extended X-ray absorption of fine structure measurements, differential thermal analysis and impedance spectroscopy. The structure of two new fluorite-related materials, Bi\(_6\)Ca\(_3\)ReO\(_{15.5}\) and Bi\(_{10}\)Ca\(_5\)ReO\(_{23.5}\), were studied. Bi\(_6\)Ca\(_3\)ReO\(_{15.5}\) formed a face-centred cubic fluorite-related structure and Bi\(_{10}\)Ca\(_5\)ReO\(_{23.5}\) a body-centred cubic material that is a 4 x 4 x 4 superstructure of the Bi\(_6\)Ca\(_3\)ReO\(_{15.5}\) phase. The structure of novel isostructural materials Bi\(_{20}\)Ca\(_7\)NbO\(_{39.5}\) and Bi\(_{10.75}\)Ca\(_{4.375}\)GaO\(_{22}\) were also investigated. Both materials formed distorted \(\delta\)-Bi\(_2\)O\(_3\) related superstructures, derived as a monoclinic supercell based on a fluorite-related hexagonal subcell. Detailed structural analysis and local environments of cations in the ordered monoclinic fluorite-related superstructure of Bi\(_9\)ReO\(_{17}\) are also explored. All materials synthesised in this thesis have structures related to that of \(\delta\)-Bi\(_2\)O\(_3\), which is known to have high oxide ion conducting properties at elevated temperatures. Oxide ion conducting properties are therefore also described.

[发布机构] University:University of Birmingham;Department:School of Chemistry

[关键词] Q Science;QD Chemistry