Sintering and properties of Li₂O · Al₂O₃ · 4SiO₂-borosilicate glass composites

Abstract

Sintering, glass crystallization, microstructure, and the resulting properties of spodumene-borosilicate glass composites were investigated. Densities >90% could be obtained for samples sintered below 1000 °C. Samples that contained more low-viscosity glass densified at lower temperatures, and significant density reduction was observed at higher temperatures. Samples that contained high-viscosity glass densified only at higher temperatures. When glasses of different viscosity were added, the densification of the composites was improved. There was interdiffusion between spodumene and glass. Cristobalite crystallized from the pure glasses. Addition of spodumene changed the major phase crystallized to anorthite or α-quartz as a result of dissolution of spodumene into glass. Composites that contained glass of higher silica content showed more crystallization. As sintering temperatures increased, the amount of crystallization decreased, due to dissolution of glass into spodumene. The spodumene particles showed angular shape with smooth and straight sides. The spodumene-glass composites showed a dielectric constant in the range of 5–6, a loss tangent generally <1%, and a CTE value in the range of 2−5.6 × 10⁻⁶ K⁻¹. Codoping of glasses with different viscosity effectively improved the densification and properties of the composites.