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

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 δ-Bi₂O₃ 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, Bi₆Ca₃ReO_15.5 and Bi₁₀Ca₅ReO_23.5, were studied. Bi₆Ca₃ReO_15.5 formed a face-centred cubic fluorite-related structure and Bi₁₀Ca₅ReO_23.5 a body-centred cubic material that is a 4 x 4 x 4 superstructure of the Bi₆Ca₃ReO_15.5 phase. The structure of novel isostructural materials Bi₂₀Ca₇NbO_39.5 and Bi_10.75Ca_4.375GaO₂₂ were also investigated. Both materials formed distorted δ-Bi₂O₃ 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 Bi₉ReO₁₇ are also explored. All materials synthesised in this thesis have structures related to that of δ-Bi₂O₃, which is known to have high oxide ion conducting properties at elevated temperatures. Oxide ion conducting properties are therefore also described.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2010

Author dc:creator

• Thompson, Maria

• QD Chemistry