Characterization and Sintering Behavior of Alkoxide‐Derived Aluminosilicate Powders

Submicrometer SiO 2 ‐Al 2 O 3 powders with compositions of 46.5 to 76.6 wt% Al 2 O 3 were prepared by hydrolysis of mixed alkoxides. Phase change, mullite composition, and particle size of powders with heating were analyzed by DTA, XRD, IR, BET, and TEM. As‐produced amorphous powders partially transformed to mullite and Al‐Si spinel at around 980°C. The compositions of mullite produced at 1400° and 1550°C were richer in Al 2 O 3 than the compositions of stable mullite solid solutions predicted from the phase diagram of the SiO 2 ‐Al 2 O 3 system. Particle size decreased with increasing Al 2 O 3 content. The sintered densities depended upon the amount of SiO 2 ‐rich glassy phase formed during sintering and the green density expressed as a function of particle size.