Glass structure and crystallization of Al and B containing glasses belonging to the Li₂O–SiO₂system

Abstract

The aim of the present work is to investigate the effect of substituting B2O3 for Al2O3 in a non-stoichiometric lithium disilicate (Li2Si2O5, LS2) glass composition belonging to the system Li2O–K2O–Al2O3–SiO2.

Influence of Al2O3 and B2O3 on Sintering and Crystallization of Lithium Silicate Glass System

“…But this is not completely true because of their differences in terms of intermolecular interactions. However, these interactions play a minor role as the changes in the system are mainly entropy driven . The presence of both Al and B together provokes larger entropy, consequently leading to stable liquid phase with less free energy, and thus there is less driving force for crystallization.…”

“…Therefore, in these Li‐rich regions with depolymerized Si units, kinetically it would be more favorable for the crystallization of LS phase to occur. Furthermore, our previous investigation of the current compositions by NMR spectroscopy elucidated that Al and B tetrahedra preferentially coordinated to highly polymerized Si units. Therefore, this leaves the depolymerized network free from dopants.…”

“…This converts the charge compensating oxide into a network modifying oxide, thus decreasing the viscosity. At room temperature the glasses showed equal concentrations of B III and B IV units . However, at higher temperatures the equilibrium could shift more toward B III units, creating even more nonbridging oxygen leading to less viscosity.…”

“…The present study aims toward investigating the effects of the partial and total substitution of Al 2 O 3 by B 2 O 3 on the sintering behavior and crystallization of glass powder compacts of a relatively simple nonstoichiometric lithium disilicate‐based glass composition in the glass‐forming region of Li 2 O–K 2 O–Al 2 O 3 –SiO 2 with SiO 2 /Li 2 O molar ratio of 3.12. This paper is a continuation of our previous work in which GCs of the same compositions were investigated addressing the influence of Al 2 O 3 and B 2 O 3 on glass network structure, liquid–liquid phase segregation, and crystal nucleation in monolithic glasses. In this paper, particular emphasis was given to the crystalline phase evolution and sintering ability of glass powders.…”

Phase and microstructural evolution in lithium silicate glass‐ceramics with externally added nucleating agent

“…In this case all three types of glasses, GC1, GC2, and GC3 indicate the presence of (AlO 4/2 ) tetrahedron in the glass structure with a peak maxima of 49.91 ppm, 49.54 ppm, and 62.83 ppm respectively. A notably more positive shift in GC3 indicates the presence of relatively more amount of (AlO 4/2 ) tetrahedral which are incorporated in the network as Q 4 species . These Al tetrahedrons form tectoaluminosilicate structure that is, a 3D framework structure of SiO 4 and Al tetrahedral (more specifically AlO 4/2 − tetrahedra) linked by corner sharing, with a negative charge arising from tetrahedral substitution of Al for Si atoms .…”