Properties of Mixed Alkali Germanate Glasses
Date
2008-04
Authors
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Journal ISSN
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Publisher
New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
Abstract
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-cesiumgermanium
ternary, the sodium-potassium-germanium ternary, and the potassiumrubidium-
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-potassiumgermanate
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.
Description
Advisory committee members: Alexis Clare, Doreen Edwards, Matthew Hall. Dissertation completed in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in Glass Science at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University
Type
Thesis