Nucleation and morphology of crystals in simple and complex silicate glasses R′2O-SiO2, R′2O-R″O-SiO2, (R′ = Li, Na, K; R″ = Ca, Mg) synthesized by the sol-gel method

Abstract

Sol-gel technology is a promising method not only to obtain the batch of the main composition but also to include low additives in glass. In this work, the batches obtained via the sol-gel method have been used to synthesize silicate glass based on the Li2O-SiO2 system with the additives of R′2O and R″O, (R′ = Na, K; R″ = Ca, Mg). The Li2O-SiO2 system without the additives R′ and R″ has been studied by us most completely. It has been determined that the main crystal phase in the glass of Li2O-SiO2 system with Li2O content up to 33 mol % is lithium disilicate, Li2O · 2SiO2. In the range of compositions from 33.8 to 40.7 mol % Li2O, solid solutions based on lithium disilicate are formed; and, starting from 40.7 mol % Li2O, solid solutions based on lithium metasilicate. The kinetic dependences of the number of nucleating lithium disilicate crystals from the time of heat treatment have been obtained at various temperatures of heat treatment. The temperature dependences of the stationary rate of nucleation of crystals have been studied. The results have been compared for the glass prepared with the use of the conventional and sol-gel method. It has been determined that the complication of the composition of glass based on 26Li2O · 74SiO2 (mol %) by the addition of R′ = Na, K; R″ = Ca, Mg affects the morphology of lithium disilicate crystals. The use of the sol-gel method of synthesis of glass leads to a more homogeneous spatial arrangement of crystals in bulk glass, the measure of which (distribution) is the dispersion of the number of traces of crystals per unit area of the section.