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

Thompson, Maria (2010). Synthesis and characterisation of d-Bi2O3 related materials stabilised by substitutions of Ca, Ga, Nb and Re. University of Birmingham. Ph.D.

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## Abstract

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.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Greaves Professor, ColinUNSPECIFIEDUNSPECIFIED
Licence:
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Chemistry
Funders: Engineering and Physical Sciences Research Council, Other
Other Funders: The University of Birmingham
Subjects: Q Science > QD Chemistry
URI: http://etheses.bham.ac.uk/id/eprint/1185

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