Preparation of lithium aluminosilicate glass-ceramic monolith from metal alkoxide solution

Abstract

Glass-ceramic monoliths with a composition of Li₂O·Al₂O₃·4SiO₂ have been synthesized by the sol-gel technique using metal alkoxides as starting materials. Heating dried gel monoliths of about 36 mm diameter and height to appropriate temperatures gave glass-ceramic monoliths of about 20 mm diameter and height without the occurrence of cracks, while a melt-derived glass body of the same composition was cracked or softened on heating. The glass-ceramic monoliths obtained by heating gel monoliths at 1000 ‡C for 40 h were a porous body, whose bulk density and porosity were 1.62 g cm⁻³ and 34%, respectively. On heating gel monoliths, Β-eucryptite crystals were first precipitated around 750 ‡C, followed by precipitation of Β-spodumene crystals at 830 ‡C. At higher temperatures the latter grew at the expense of the former phase. The crystallized specimens exhibited very low thermal expansion coefficient ranging from −13-12×10⁻⁷ ‡C⁻¹ at temperatures from room temperature to 700 ‡C depending on the heat-treatment temperature of gels, indicating that a porous glass-ceramic monolith with ultra-low thermal expansion can be prepared using the present sol-gel method.