Crystallization pathways and some properties of lithium disilicate oxynitride glasses

Abstract

Lithium silicates have been used as model glasses for scientific and technological studies of glass-ceramics because they easily crystallize in the interiors, even without the addition of any nucleating agent. On the other hand, partial replacement of oxygens with nitrogens affects most properties of oxide glasses, but its effect on the crystallization kinetics of the glasses has been poorly documented. In this work, we report, for the first time, on the crystallization kinetics of nitrited lithium silicate glasses. The oxynitride glasses were prepared by partial substitution of oxygen by nitrogen, up to 6 at.% N/(N+O), by melt-quenching the liquid under N 2 atmosphere inside a glove box. As expected, the density, microhardness, and Young's modulus of the glasses improved with increasing nitrogen content. Higher values of glass transition and crystallization peak temperatures were also obtained with an increase in the nitrogen content. Rietveld refinement analysis after adequate thermal treatment revealed that addition of nitrogen led to increasingly higher contents of lithium metasilicate at the expense of the (expected) lithium disilicate crystal phase. Crystallization kinetic parameters such as the activation energy and 2 Avrami index were calculated using Ozawa's equations. These two parameters also increased with increasing nitrogen content, whereas the crystal growth rates decreased with increasing nitrogen content. The above-described changes in the properties of the oxynitride glasses are straightforwardly explained by the increase in the connectivity of the glass network, which results in enhancement of the atomic packing density owing to partial substitution of twocoordinated oxygens by three-coordinated nitrogens.

Structure and ionic conductivity of nitrated lithium disilicate (LiSiON) glasses

“…All glasses were annealed at 400 o C for 2 h, which is well below the glass transition temperature to avoid any crystallization process. T g and T p increased with the addition of nitrogen and are reported elsewhere [16].…”

Review: Elaboration, structure, and mechanical properties of oxynitride glasses

“…In most cases, devitrification occurs through a self‐nucleation process, which was attributed to the presence of metallic nano/micro‐particles resulting from the decomposition of Si 3 N 4 4,203 . The crystal growth rate was observed to decrease with increasing nitrogen content in Li–Si–O–N glasses, likely because of the increase cross‐linking and stability of the glass network in the presence of nitrogen 204,205 …”

“…4,203 The crystal growth rate was F I G U R E 1 9 Shear viscosity coefficient, η, of glasses from different chemical systems observed to decrease with increasing nitrogen content in Li-Si-O-N glasses, likely because of the increase crosslinking and stability of the glass network in the presence of nitrogen. 204,205 A change in the nitrogen source (AlN or Si 3 N 4 ) leads to different crystalline phases. 151,206 Nitrogen is eventually found to have some incidence on both the relative fractions and the structures of the different phases.…”

“…151,206 Nitrogen is eventually found to have some incidence on both the relative fractions and the structures of the different phases. 206,207 Depending on the composition, nitrogen may either not enter the crystallized phases 100,205 or lead to the crystallization of oxynitrides 151,118,187,[208][209][210][211] or nitrides (such as ZrN). 212 The elastic moduli, hardness, and fracture toughness of the resulting oxynitride glass-ceramics are typically improved by 25% in comparison to the oxynitride parent glass.…”