Abstract
In glass materials, Poisson’s ratio (ν) has been proposed to be correlated with a variety of features, including atomic packing density (Cg), liquid fragility (m), and network connectivity. To further investigate these correlations in oxide glasses, here, we study cesium borate and cesium silicate glasses with varying modifier/former ratio given the difference in network former coordination and because cesium results in relatively high ν compared to the smaller alkali modifiers. Within the binary glass series, we find positive correlations between ν on one hand and m and Cg on the other hand. The network former is found to greatly influence the correlation between ν and the number of bridging oxygens (nBO), with a negative correlation for silicate glasses and positive correlation for borate glasses. An analysis based on topological constraint theory shows that this difference cannot be explained by the effect of superstructural units on the network connectivity in lithium borate glasses. Considering a wider range of oxide glasses from the literature, we find that ν generally decreases with increasing network connectivity, but with notable exceptions for heavy alkali borate glasses and calcium alumino tectosilicate glasses.
Highlights
Oxide glasses are well-known for their brittle fracture behavior, limiting current and emerging applications [1,2,3,4]
Glasses with low ν are generally more prone to undergo a high degree of densification during indentation [5]—we here note that homogeneous oxide glasses only exhibit positive values of ν, negative ν is possible in other material families [6]
The silicate network becomes increasingly depolymerized with increasing cesium content visible by the decrease in Q4 species (Supplementary Figure S1) and, an increase in Q3 species
Summary
Oxide glasses are well-known for their brittle fracture behavior, limiting current and emerging applications [1,2,3,4]. The deformation behavior of isotropic glasses, even beyond the elastic limit, has been proposed to be closely related to Poisson’s ratio (ν), which is defined as the negative ratio of the transverse strain relative to the longitudinal strain in the elastic loading direction. When subjected to high pressure, silica becomes densified (larger Cg ) and the Poisson’s ratio increases [8]. Another interesting proposed correlation is that between ν and fracture energy, with an abrupt brittle-to-ductile transition at ν = 0.32 for various glassy systems [7,9,10,11].
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