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Title: Characterisation of novel antimony (III) oxide-containing glasses
Author: Orman, Robin George
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2010
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The structures of several glass systems containing the lone-pair cation Sb3+ have been studied using a range of techniques, including neutron diraction, Mössbauer spectroscopy, Raman spectroscopy, energy-dispersive X-ray (EDX) analysis, X-ray diraction and density measurements. Comparisons with some related crystals have also been used to identify structural features. An Sb2O3 glass was prepared by roller-quenching and found to be both fully amorphous and free of contaminants, using X-ray diraction and EDX analysis, respectively. A glass transition temperature, Tg, of 250(2) °C and a crystallisation temperature, Tc, of 303(2) °C were measured using dierential scanning calorimetry, whilst the density of the glass was found to be 5:27(2) g cm3. Analysis of the total correlation function T(r) from neutron diraction of the sample found two distinct peaks at 1:972(1)Å and 2:092(4) Å, with a total Sb-O coordination number of 3:24(4), indicating the presence of some [Sb3+O4] and/or [Sb5+O6] units, in addition to the main [Sb3+O3] network. Several models of the local structure are proposed, based on dierent possible amounts of Sb5+ present in the glass. An antimony oxychloride glass was prepared from crystalline Sb8O11Cl2 by splatquenching, and Mössbauer spectroscopy was used to determine that it contained no Sb5+. The thermal events in the system were characterised, with Tg = 278(2) °C and Tc = 318(2) °C; the density was found to be 5:10(2) g cm3. Neutron diraction of the crystal distinguished between two dierent structural models in the literature, whilst also indicating that the glass may consist of similar chains of [Sb3+O3] and [Sb3+O4] units. Glasses of nominal composition x Sb2O3 . (1 - x) B2O3 were studied over the range x = 0:1 to x = 0:7. Raman spectroscopy and neutron diraction indicated that the glass network consists of significant amounts of [B3O6] boroxol rings at low x that are cleaved by the introduction of [Sb3+O3] trigonal pyramids. At higher x, there is some evidence for Sb-O-Sb bonding, resulting in the persistence of the boroxol rings to x - 0:7. Two Sb-O distances were apparent in the T(r), suggesting similar models of the antimony oxide units to those for the Sb2O3 glass. Five antimony silicate glasses of nominal composition x Sb2O3 . (1 - x) SiO2 were prepared and found by Mössbauer spectroscopy to contain growing amounts of Sb5+ with increasing x, up to 9:9(5)% at x = 0:8. Density measurements suggested that the SiO2 and Sb2O3 networks mix in the glass without significantly altering each other, and this is supported by comparison of the measured neutron diraction T(r) with a weighted sum of the total correlation functions of the two system end-members. The simulation also indicated fewer high-coordination antimony oxide units ([Sb 3+O4], [Sb5+O6]) than in the Sb2O3 glass, although two distinct Sb-O distances were once again apparent in the neutron T(r). The overall conclusion is that Sb2O3 forms a glass network consisting predominantly of [Sb3+O3] trigonal pyramids with a stereochemically-active lone-pair, whilst some more highly-coordinated [Sb3+O4] and [Sb5+O6] units may also be present.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council (Great Britain) (EPSRC) ; University of Warwick (UoW)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics