Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B, 2020
Tellurite glasses, made from the conditional glass former TeO2, show potential for use in optical... more Tellurite glasses, made from the conditional glass former TeO2, show potential for use in optical applications. Alkali and alkaline earth tellurite glasses, along with single component, rapidly cooled, TeO2 are reported and studied here. Thermal properties of boron, potassium, lithium, sodium, rubidium, cesium, barium, and strontium tellurites were obtained via differential scanning calorimetry and related to structural changes observed using Raman spectroscopy. Additionally, coordination numbers of barium and strontium tellurites versus amount of modifier are also calculated. By understanding the thermal properties and coordination numbers of alkali and alkaline earth tellurites, the goal is to better elucidate the structure of amorphous TeO2.
ABSTRACT Alkali borosilicate glasses have been prepared with the general composition RM2O·B2O3·KS... more ABSTRACT Alkali borosilicate glasses have been prepared with the general composition RM2O·B2O3·KSiO2, where M is an alkali metal (lithium, sodium or potassium), R represents the molar ratio of alkali oxide to boron oxide and K represents the molar ratio of silicon dioxide to boron oxide. 29Si magic angle spinning-nuclear magnetic resonance (MAS-NMR) was performed on these glasses to examine the short-range order about the silicon atoms. In this paper, the resultant chemical shift data of these glass families were combined and examined in the light of various models derived from both 11B and 29Si NMR for the sharing of alkali oxide between the borate and silicate glass networks. These models all define an R value, R0, below which the alkali oxide is entirely associated with the borate network, and above which the alkali oxide is shared proportionally between the two glass networks. By combining the data from the three glass families, the model with R0 optimized as a function of K was shown to provide an extremely good fit to the experimental data, while promising to reconcile both the 11B and 29Si NMR data. Of the three alkali borosilicate families studied, only the potassium borosilicates showed the effect of CO2 retention from the alkali carbonate starting materials on the 29Si NMR spectra.
High-resolution x-ray pair distribution functions for molten and glassy TeO2 reveal coordination ... more High-resolution x-ray pair distribution functions for molten and glassy TeO2 reveal coordination numbers nTeO ≈ 4. However, distinct from the known α-, β- and γ-TeO2 polymorphs, there is considerable short-range disorder such that no clear cutoff distance between bonded and non-bonded interactions exists. We suggest that this is similar to disorder in δ-TeO2 and arises from a broad distribution of asymmetric Te-O-Te bridges, something that we observe becomes increasingly asymmetric with increasing liquid temperature. Such behavior is qualitatively consistent with existing interpretations of Raman scattering spectra, and equivalent to temperature-induced coordination number reduction, for sufficiently large cutoff radii. Therefore, TeO2 contains a distribution of local environments that are, furthermore, temperature dependent, making it distinct from the canonical single-oxide glass formers. Our results are in good agreement with high-level ab initio cluster calculations.
Abstract : Novel methods for the preparation of 0-17 labelled ionic oxide glasses which are label... more Abstract : Novel methods for the preparation of 0-17 labelled ionic oxide glasses which are label conservative and yield glasses at the same enrichment level as the starting materials, were designed to provide materials for the investigation of the 0-17 NMR and the vibrational spectra. These methods are detailed for both oxygen-labelled network formers, B2O3 and SiO2, and network modifiers, Li2O and LiO H. Routes are suggested for related network formers and modifiers. (Author)
Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B, 2020
Tellurite glasses, made from the conditional glass former TeO2, show potential for use in optical... more Tellurite glasses, made from the conditional glass former TeO2, show potential for use in optical applications. Alkali and alkaline earth tellurite glasses, along with single component, rapidly cooled, TeO2 are reported and studied here. Thermal properties of boron, potassium, lithium, sodium, rubidium, cesium, barium, and strontium tellurites were obtained via differential scanning calorimetry and related to structural changes observed using Raman spectroscopy. Additionally, coordination numbers of barium and strontium tellurites versus amount of modifier are also calculated. By understanding the thermal properties and coordination numbers of alkali and alkaline earth tellurites, the goal is to better elucidate the structure of amorphous TeO2.
ABSTRACT Alkali borosilicate glasses have been prepared with the general composition RM2O·B2O3·KS... more ABSTRACT Alkali borosilicate glasses have been prepared with the general composition RM2O·B2O3·KSiO2, where M is an alkali metal (lithium, sodium or potassium), R represents the molar ratio of alkali oxide to boron oxide and K represents the molar ratio of silicon dioxide to boron oxide. 29Si magic angle spinning-nuclear magnetic resonance (MAS-NMR) was performed on these glasses to examine the short-range order about the silicon atoms. In this paper, the resultant chemical shift data of these glass families were combined and examined in the light of various models derived from both 11B and 29Si NMR for the sharing of alkali oxide between the borate and silicate glass networks. These models all define an R value, R0, below which the alkali oxide is entirely associated with the borate network, and above which the alkali oxide is shared proportionally between the two glass networks. By combining the data from the three glass families, the model with R0 optimized as a function of K was shown to provide an extremely good fit to the experimental data, while promising to reconcile both the 11B and 29Si NMR data. Of the three alkali borosilicate families studied, only the potassium borosilicates showed the effect of CO2 retention from the alkali carbonate starting materials on the 29Si NMR spectra.
High-resolution x-ray pair distribution functions for molten and glassy TeO2 reveal coordination ... more High-resolution x-ray pair distribution functions for molten and glassy TeO2 reveal coordination numbers nTeO ≈ 4. However, distinct from the known α-, β- and γ-TeO2 polymorphs, there is considerable short-range disorder such that no clear cutoff distance between bonded and non-bonded interactions exists. We suggest that this is similar to disorder in δ-TeO2 and arises from a broad distribution of asymmetric Te-O-Te bridges, something that we observe becomes increasingly asymmetric with increasing liquid temperature. Such behavior is qualitatively consistent with existing interpretations of Raman scattering spectra, and equivalent to temperature-induced coordination number reduction, for sufficiently large cutoff radii. Therefore, TeO2 contains a distribution of local environments that are, furthermore, temperature dependent, making it distinct from the canonical single-oxide glass formers. Our results are in good agreement with high-level ab initio cluster calculations.
Abstract : Novel methods for the preparation of 0-17 labelled ionic oxide glasses which are label... more Abstract : Novel methods for the preparation of 0-17 labelled ionic oxide glasses which are label conservative and yield glasses at the same enrichment level as the starting materials, were designed to provide materials for the investigation of the 0-17 NMR and the vibrational spectra. These methods are detailed for both oxygen-labelled network formers, B2O3 and SiO2, and network modifiers, Li2O and LiO H. Routes are suggested for related network formers and modifiers. (Author)
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