The synthesis and characterisation of pyrochlore frameworks

Structural studies have been undertaken on a wide range of pyrochlore phases, with a<br/>focus on garnering a better understanding of the factors determining the formation and<br/>behavior of these materials. Extensive structural characterisation has been undertaken<br/>primarily using powder X-ray and powder neutron diffraction techniques to explore the<br/>subtle structural changes that occur as a result of changes in composition on the two<br/>interlocking networks that make up the pyrochlore structure.<br/><br/>Particular attention has been paid to hydrated beta-pyrochlore materials, using high<br/>resolution TOF and constant wavelength PND to accurately determine the location and<br/>orientation of the water molecules within the structure. The location of these molecules<br/>has been shown to be directly correlated to the overall lattice dimensions of the<br/>pyrochlore framework, with the subsequent molecular orientation and internal bond<br/>angles changing to provide an optimum stabilization effect on the A-site cation.<br/>Investigation into the effects of hydration upon the superconducting beta-pyrochlore<br/>series AOs2O6.nH2O (where A = K, Rb and Cs) has also been investigated; with a<br/>correlation between the structural changes, the degree of hydration and the onset of the<br/>superconducting state being discussed.<br/><br/>Also presented is work seeking to determine the scope and effects of ion-exchange on<br/>the A2O’ network of the pyrochlore framework, with several new phases synthesised and<br/>other known phases extensively characterized along with a discussion regarding the<br/>limits of what may be included in the pyrochlore framework.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2010

Author dc:creator

• Simon, Charles Francis

Advisor dc:contributor.advisor

• Weller, Mark