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dc.contributor.advisorIrvine, John T. S.
dc.contributor.advisorJones, Martin Owen
dc.contributor.authorIrvine, Gavin John
dc.description.abstractThis thesis presents research into two superionic conductors: BaH₂ and β-Ca₂NH. The research presented herein explores the diffusion pathway of hydride ions (H⁻) in the solid-state of these materials. Using novel combined spectroscopic techniques, we show that BaH₂ has a diffusion pathway that involves the partial melting of its crystal lattice. This "liquid-like" sublattice is analysed in detail in order to elucidate the origins of such behaviour as well as provide a physical description of a sublattice manifesting as "liquid-like." The second material explored in this thesis is a novel superionic conductor not previously published, β-Ca2NH. The analysis shows that Ca₂NH (nitride- hydride) materials come in at least two distinct polymorphs, with dramatically different ionic conductivities. Using in situ neutron powder diffraction along with several other techniques, we explore the unique configurations of the different Ca₂NH polymorphs and identify what gives rise to ionic conductivity in one form and not the other. Furthermore, Ca₂NH is contrasted to the closely related imide (NH₂⁻) and amide (NH₂⁻). Barium hydride is shown to have an ionic conductivity of 0.32 S/cm at 600 ◦C and its conduction due to the presence of a liquid-like sublattice. Calcium nitride-hydride, on the other hand, is shown to have an ionic conductivity of 0.08 S/cm at 600 ◦C and its conduction defined by an intrinsic vacancy concentration created by anti-Frenkel defects. Thus, the thesis explores two excellent solid-state ionic conductors with dramatically different ionic conduction mechanisms. The synthesis route for the following compounds are detailed in this thesis: BaH₂, BaD₂, Ca₂NH - both polymorphs, CaNH, and Ca(NH₂)₂.en_US
dc.description.sponsorship"I want to acknowledge ISIS Neutron and Muon Spallation Source for their funding of this project (agreement number STFC: 5005) … I want to thank the James E Crockett Scholarship for the help in funding this PhD. Without their contribution, I am sure this project would not have been available."--Acknowledgementsen
dc.publisherUniversity of St Andrews
dc.rightsCreative Commons Attribution-NoDerivatives 4.0 International*
dc.subjectSuperionic conductoren_US
dc.subjectNeutron scatteringen_US
dc.subjectTotal scatteringen_US
dc.subjectIonic conductivityen_US
dc.subjectConcerted migrationen_US
dc.subjectVacancy mediated conductivityen_US
dc.subjectLiquid-like sublatticeen_US
dc.subject.lcshElectric conductorsen
dc.subject.lcshSpectrum analysisen
dc.titleStudies of hydride ion conductors using combined spectroscopy techniquesen_US
dc.contributor.sponsorUK Research and Innovation (Agency). ISIS Neutron and Muon Sourceen_US
dc.contributor.sponsorJames E. Crockett Educational & Charitable Trusten_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US
dc.publisher.departmentRutherford Appleton Laboratory, STFCen_US
dc.rights.embargoreasonEmbargo period has ended, thesis made available in accordance with University regulationsen

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    Except where otherwise noted within the work, this item's licence for re-use is described as Creative Commons Attribution-NoDerivatives 4.0 International