SAXS analysis of textures formed by phase separation and crystallization of Al2O3–SiO2 glasses

Textures formed by phase separation and crystallization of Al2O3–SiO2 glasses with 15, 25 and 50 mol% Al2O3 compositions were investigated by small angle X-ray scattering (SAXS) and TEM. From the Porod analysis of the SAXS patterns, droplet structures were found in glasses with 15 and 50 mol% Al2O3 compositions, whereas an interconnected structure was formed by spinodal decomposition in the glass with 25 mol% Al2O3. In the initial-stage crystallization of mullite, nucleation was considered to occur in the Al2O3-rich regions. The crystallites of mullite were of similar size to the phase separated region. The relationship between the annealing time and the size of the interconnected texture formed by spinodal decomposition was analyzed using Cahnʹs theory, giving good agreement with the result obtained by the Porod method. The distance distribution of the phase separated grains was obtained from the radial distribution function calculated by Fourier transformation of the SAXS patterns. The calculated intergrain distances increased with increasing annealing time and were in good agreement with those obtained from TEM observation.