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

Textures formed by phase separation and crystallization of Al2O3-SiO2 glass es with 15, 25 and 50 mol% Al2O3 compositions were investigated by small an gle X-rap scattering (SAXS) and TEM. From the Pored analysis of the SAXS pa tterns, droplet structures were found in glasses with Ii and 50 mol% Al2O3 compositions, whereas an interconnected structure was formed by spinodal de composition in the glass with 25 mol% Al2O3. In the initial-stage crystalli zation of mullite, nucleation was considered to occur in the Al2O3-rich reg ions. The crystallites of mullite were of similar size to the phase separat ed region. The relationship between the annealing time and the size of the interconnected texture formed by spinodal decomposition was analyzed using Cahn's theory, giving good agreement with the result obtained by the Pored method. The distance distribution of the phase separated grains was obtaine d from the radial distribution function calculated by Fourier transformatio n of the SAXS patterns. The calculated intergrain distances increased with increasing annealing time and were in good agreement with those obtained fr om TER I observation. (C) 2001 Elsevier Science B.V. All rights reserved.