The solid solution range of melt‐grown mullite was examined by crystal‐chemical methods. The maximum Al2O3 content as determined by EDX was ∼83.6 wt%, 75 mol%, or the nominal composition 3Al2O3.SiO2. For samples of overall composition 81 to 83 wt% Al2O3, extra lines indicating crystallographic superstructure appeared in Guinier X‐ray patterns. The corresponding TEM microstructure consisted of a mullite matrix finely twinned on (001), the twins being 0.02 to 0.10 μm wide, with oriented exsolution of α‐A12O3, often twinned, also being present. The analogy between mullite superstructure and that of plagioclase feldspars, as well as the relevance of these findings to the SiO2‐Al2O3 metastable phase equilibria are discussed.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of the American Ceramic Society|
|State||Published - Sep 1983|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry