Diffusion kinetics and structural properties of chemically strengthened titania-doped soda-lime silicate glasses were studied by depth-resolved X-ray photoelectron spectroscopy, Raman spectroscopy and spectrophotometry. The glasses were ion exchanged, whereby Na+ in the glass was replaced by K+ in a molten salt bath, at four different treatment temperatures between 350 and 500 °C. The alkali diffusion coefficient, DK-Na, and corresponding activation energy were calculated to be between 3.26×10−12 and 4.47×10−11 cm2s−1 and between 101.1 kJmol−1 and 105.6 kJmol−1, respectively. DK-Na was observed to decrease as the TiO2 concentration was increased. Raman analysis showed Q3-silicate species with different bond lengths, which was attributed to surface compressive stresses, and increasing Si-O-Si bond angle with increasing ion exchange temperature. Ti3+ ions exist as a minor species in the glasses and its concentration depends on the TiO2 content. Deconvolution of the optical absorption spectra reveals Jahn-Teller compressive distortion of the Ti3+ octahedral coordination.

The preceding part [M. Edén, J. Non.-Cryst. Solids, 357, (2011) 1595-1602] introduced the "split network" strategy for estimating the network polymerization degree (r A) and mean number of bridging oxygen (BO) atoms (N̄BOA) for a network former A, given that these parameters are known for all other network builders in the multi-component oxide glass. However, as the detailed ordering of BO and non-bridging oxygen (NBO) species is often difficult to assess experimentally, we summarize some "rules of thumb" for predicting the coordination number and tendency to accept NBO ions for Al 3+, B 3+, Si 4+ and P 5+ cations: they are helpful in scenarios devoid of experimental data. Using the parameters r and N̄BO, we present expressions for the BO/NBO distributions among tetrahedrally coordinated cations, as predicted from the binary and random models. Multinuclear 11B, 27Al and 29Si solid-state NMR is exploited to derive the split network representations of a set of Na-Ca-(Al)-(B)-Si-O glasses. These results are subsequently used to gain structural insight into two commercial glass-wool fibers that constitute alumino-borosilicate networks modified by Na +, K +, Ca 2+ and Mg 2+ ions. © 2010 Elsevier B.V.

Adding alumina to the conventional soda lime silicate glass composition improves many properties, however, also increases the melting temperature. In the current paper, alumina doping of soda lime silicate glasses and its implications to high temperature viscosity are investigated in order to verify the linearity when replacing SiO₂ for Al₂O₃. An anomaly in the linearly increasing viscosity was found when the ratio CaO/Al₂O₃ is <1, which is explained by Ca²⁺ acting as an inhibitor for viscous flow. The Angell and Rao and the Waterton-MYEGA models show very similar results, even for the extrapolated Tg. Thermodynamic data extracted using the Ojovan method generally increases linearly with the Al₂O₃ content. The Doremus fragility index shows a deviation in the linearity while the Angell fragility index on the other hand shows a linear increase with the Al₂O₃ content.

Titania represents an important compound for property modifications in the widespread family of soda lime silicate glasses. In particular, such titania-containing glasses offer interesting optical and mechanical properties, for example, for substituting lead-bearing consumer glasses. Here, we provide a systematic study of the effect of TiO₂ on the structural, thermal, and mechanical properties for three series of quaternary Na₂O–CaO–TiO₂–SiO₂ glasses with TiO₂ concentrations up to 12 mol% and variable Na₂O, CaO, and SiO₂ contents. Structural analyses by Raman and magic-angle spinning ²⁹Si NMR spectroscopy reveal the presence of predominantly four-fold coordinated Ti^[4] atoms in glasses of low and moderate TiO₂ concentrations, where Si–O–Si bonds are replaced by Si–O–Ti^[4] bonds that form a network of interconnected TiO₄ and SiO₄ tetrahedra, with a majority of the non-bridging oxygen ions likely being located at the SiO₄ tetrahedra. At higher TiO₂ contents, TiO₅ polyhedra are also formed. Incorporation of TiO₂ strongly affects the titanosilicate network connectivity, especially when its addition is accompanied by a decrease of the CaO content. However, except for the thermal expansion coefficient, these silicate-network modifications seem to have no impact on the thermal and mechanical stability. Instead, the compositional dependence of the thermal and mechanical properties on the TiO₂ content stems from its effect on the network energy and packing efficiency.

The concentration and temperature ranges of liquid crystal and glass formation in binary systems of cobalt (II) caprylate with either lithium or lead caplylates have been studied by differential thermal analysis and optical polarization microscopy. Absorption spectra of Co(II) cations in mesophases and glasses of these binary caprylate systems have been analyzed as a function of temperature and composition to get information on the coordination of Co(II) ions. For the binary system of lead-cobalt caprylate. we found that the Co(II) ions are octahedrally coordinated over the range of temperatures and compositions studied, whereas in the binary lithium-lead caprylate system. the Co(II) ions can exist in both octahedral and tetrahedral coordination depending on composition and temperature. Thermochromic behavior was observed for all compositions studied here, from blue to violet and pink, depending on the composition and temperature of the system studied. An unusual increase of optical density with decreased Co(II) ion concentration has been observed for the Co-Li caprylate binary system up to 50 mol%. An increasingly ionic Co(II) coordination environment as Li ion concentration increases facilitates a concomitant increase in the proportion of more optically dense tetrahedrally coordinated Co(II) ions.