EFFECT OF AN INCREASE IN THE SODIUM AND LITHIUM OXIDES CONTENT ON THE PROCESS OF CRYSTALLIZATION OF GLASSES IN THE Li<sub>2</sub>O-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> SYSTEM
In this work, glasses were synthesized based on the ternary system Li2O-Al2O3-SiO2 (LAS). The composition was modified by increasing the total concentration of alkali oxides, which made it possible to reduce the synthesis temperature to 1580 ͦС. X-ray phase analysis and dilatometric measurements have shown that the growth of LiAlSi3O8 solid solutions with a negative CTE occurs at temperatures close to the glass transition temperature in a limited time interval, which leads to an insignificant decrease in the CTE of glass ceramics. It has been found that an increase in the time and temperature of heat treatment leads to the growth of LiAlSi2O6 spodumen nanocrystals. Thus, the introduction of high concentrations of alkali oxides does not allow achieving the desired effect of lowering the thermal expansion coefficient