Lithium aluminium silicate–based low–coefficient of thermal expansion materials obtained by colloidal and low–temperature approaches

Abstract

Glass ceramics based on lithium aluminosilicates are interesting because they have low coefficients of thermal expansion (CTEs) and are adjustable to different processes by adjusting their chemical composition. However, their typical production is complex, requiring high process temperatures and long grinding times to obtain micrometric particles. This study presents the synthesis of low–CTE lithium aluminium silicate nanoparticles obtained through a colloidal approach from the heterocoagulation of a lithium source (lithium acetate obtained by the reaction of carbonate with acetic acid), silica, and alumina from different sizes. The concentrated suspensions were dried, and the powders were thermally treated at 750–900 °C to form the crystalline phases projected by the solid–state reaction. The samples were characterized by thermal and structural analysis. The use of alumina nanoparticles in the synthesis of powders yielded mostly the crystalline phases β–spodumene and β–eucryptite, which were thermally treated at 850 °C and showed a low CTE (1.25 × 10−6 °C−1). Powders were successfully synthesized, which with some adjustments in the synthesis conditions may yield higher levels of β–eucryptite and therefore much lower CTE powders.