Characterisation of novel antimony (III) oxide-containing glasses

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

Characterisation of novel antimony (III) oxide-containing glasses

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.EThOS - Electronic Theses Online ServiceEngineering and Physical Sciences Research Council (Great Britain) (EPSRC)University of Warwick (UoW)GBUnited Kingdo

Towards improved cover glasses for photovoltaic devices

For the solar energy industry to increase its competitiveness there is a global drive to lower the cost of solar generated electricity. Photovoltaic (PV) module assembly is material-demanding and the cover glass constitutes a significant proportion of the cost. Currently, 3 mm thick glass is the predominant cover material for PV modules, accounting for 10-25% of the total cost. Here we review the state-of-the-art of cover glasses for PV modules and present our recent results for improvement of the glass. These improvements were demonstrated in terms of mechanical, chemical and optical properties by optimizing the glass composition, including addition of novel dopants, to produce cover glasses that can provide: (i) enhanced UV protection of polymeric PV module components, potentially increasing module service lifetimes; (ii) re-emission of a proportion of the absorbed UV photon energy as visible photons capable of being absorbed by the solar cells, thereby increasing PV module efficiencies; (iii) Successful laboratory-scale demonstration of proof-of-concept, with increases of 1-6% in Isc and 1-8% Ipm. Improvements in both chemical and crack resistance of the cover glass were also achieved through modest chemical reformulation, highlighting what may be achievable within existing manufacturing technology constraints

Simultaneous chemical vapor deposition and thermal strengthening of glass

In the current paper we present a concept combining metal organic chemical vapor deposition with thermal strengthening process of flat glass. As the flat glass is heated to be thermally strengthened, which takes up to 20 minutes, there is an opportunity for performing a surface modification. We describe the application of transparent and amorphous Al2O3 thin films during the thermal strengthening process. Al2O3 was chosen due to the following desirable properties: increased surface mechanical properties and increased chemical durability, the latter has not been investigated in the current paper. The residual surface compressive stresses after performed strengthening of the coated glasses were quantified to be in the range of 80–110 MPa. The Al2O3 content in the surface was measured using the Surface Ablation Cell employed with Inductively Coupled Plasma Atomic Emission Spectroscopy and found to be at least doubled at the surface and having an increased Al2O3 content at least 0.5 μm underneath the glass surface. During the surface reaction, sodium is migrating to the surface giving a hazy salt layer on the glass which can easily be washed off with water. The applied coatings are transparent and provide increased surface hardness and crack resistance at low indentation loads. At higher indentation loads the interaction volume is larger and displays the same effect on the surface mechanical properties as for thermally strengthened glass. The contact angle with water compared to annealed float glass is significantly increased from 5° to 45° due to the different surface chemistry and surface topography

Terminal oxygens in amorphous TeO2

Understanding the structure of single-component glasses is essential for developing structural models of more complex multicomponent glasses. Currently, such models for tellurite systems are purely qualitative. This study presents neutron diffraction and Raman spectroscopy measurements of the structure of pure amorphous TeO2, showing that it is formed from a combination of two-thirds [TeO4] pseudo-trigonal bipyramids and one-third [TeO3] trigonal pyramids with a terminal oxygen. This is in contrast to all crystalline polymorphs of TeO2, which are formed solely from the four-coordinated units. Using this result, a quantitative model has been developed that successfully predicts the average Te–O coordination number, nTeO, for a series of potassium tellurite glasses, xK2O·(100 – x)TeO2. The observed nTeO is constant up to 15 mol % K2O due to the presence of terminal oxygen atoms in the tellurite network