| There is little data in the literature pertaining to mixed alkali germanate glasses. The majority of the data exists for the sodium-potassium-germanate glasses, and focuses on the density, glass transition temperature and vibrational spectra. This study explores three of the ten possible mixed alkali germanate glass systems: the lithium-cesium-germanium ternary, the sodium-potassium-germanium ternary, and the potassium-rubidium-germanium ternary. The mixed alkali effect was examined at two different concentrations of germania (85 and 90 mol %). To examine the mixed alkali effect on the germanate anomaly, the alkali oxides were held in a ratio of 1:1 and the germanium was varied from 100 to 75 mol %.;The glass transition temperature and densities behavior of the mixed alkali germanate glasses in this study behaved as expected, exhibiting a maximum in Tg and no mixed alkali effect in density. The glasses with a 1:1 ratio of alkali exhibited properties between the end member glasses.;The infrared spectra from this study show that the hydroxyl content increases as the amount of alkali in the glass increases. The cation identity does effect the band positions and intensities. The infrared bands between 1500 and 4000 cm-1 are shown to be a result of water.;Electrical conductivity of mixed alkali germanate glasses exhibited unique behavior. Small additions of alkali (≤ 5 mol %) result in a positive or a linear deviation from additivity, in both the lithium-cesium-germanate system and the sodium-potassium-germanate system. With 10 mol % alkali oxide addition the deviation from additivity increases as the radius ratio of the cations increases. However, with 15 mol % alkali oxide addition, the greater the difference in the radius ratio of the cations, the smaller the deviation from additivity.;A Kissinger study on the lithium-cesium-germanate glasses, yields activation energies consistent with crystallization studies in the literature for other mixed alkali germanate glasses. Glasses with a 1:1 ratio of cesium oxide to lithium oxide, or more cesium oxide than lithium oxide, crystallize into cesium germanium oxide crystals, however if there is more lithium the glasses crystallize into an unknown phase. |
