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Structural properties of solid ionic halides.

Demetriou, Demetrios Zacharia; (1991) Structural properties of solid ionic halides. Doctoral thesis (Ph.D.), University College London. Green open access

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In this thesis the structural properties of solid ionic halides and in particular several classes of fluorite structured materials have been investigated. The systems studied include: rare-earth fluorides and the anion excess alkaline earth fluorides, perovskite and elpasolite structured halides. The aim of this work is to understand and investigate: 1) The complex defect structures of the CaF2 - (Ln)F3 systems where Ln = La, Er and Nd. Chapter 3 of this thesis determines the effects of ageing (investigated by annealing samples at high temperatures for variable times) and dopant ion radius on the defect structures of the solid solutions of composition 95- 50 mole per cent CaF2-(Ln)F3. The prepared and annealed compounds of all the three systems where characterized by X-ray powder diffraction. 2) The anion disorder of the perovskite fluoride KCaF3. Chapter 4 describes a series of experiments using single crystal neutron diffraction on the D9 diffractometer at the ILL. The aim is to identify the nature and concentration of these defects, as has been achieved using single crystal neutron techniques for the high temperature superionic fluorites. This experiment therefore has offered an excellent opportunity to investigate a simple member of a potentially larger and important class of high temperature superionics. Several elpasolite structured halides, of general formula A2BReX6 (where A and B are monovalent ions and Re is a rare-earth cation). We present in Chapter 5 a study of several members of the A2BReX6 system which have been investigated by High Resolution X-ray Diffraction using the synchrotron radiation source at the Daresbury Laboratory. This work provides a basis for the further systematic investigation of these systems.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: Structural properties of solid ionic halides.
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis Digitised by Proquest.
URI: https://discovery.ucl.ac.uk/id/eprint/10124559
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