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Principles of Topological Constraint Theory (TCT) were applied to alkali borate and silicate glass systems using intermediate range structural models over wide compositional ranges. The structural model for lithium borate was derived from the Feller, Dell, and Bray model [1] and extended to the terminal composition at R = 3 where R is the molar ratio of lithium oxide to borate. The sodium borate structural model was built using both NMR [2] and Raman [3] data, and also included carbonate retention in the glass [4]. This model was extended to R = 3 similarly to the lithium borate system. The silicate system models were created from 29Si NMR data [5] and also incorporated carbonate retention where necessary [6]. Constraint models considered the effect of intermediate range structures on the system, and also incorporated the effect of “loose” alkali which is not directly associated with a non-bridging oxygen. Constraint models of the alkali borate, silicate, and borosilicate systems were then used to predict properties such as glass transition temperature and fragility. 

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.