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- Title
Strontium Dialuminate SrAl[sub4]O[sub7]: Synthesis and Stability.
- Authors
Capron, Mickael; Douy, Andre
- Abstract
Up to now, strontium dialuminate, SrAl[sub 4]O[sub 7] (SA[sub 2]), could be synthesized only by solidification from the high-temperature liquid state. We describe its synthesis from a spray-dried amorphous precursor, and specify its stability domains. Its kinetics of formation is very low. It can be crystallized in the 900-1000°C temperature range either directly with a low heating rate or via two metastable solid solutions—hexagonal strontium monoaluminate (SrAl[sub 2]O[sub 4] (SA)) and γ-alumina—by annealing at 950-1000°C. As the temperature is raised beyond 1100[sub C], SA[sub 2] becomes metastable, its formation is no longer possible, and the crystallization of Sr[sub 4]Al[sub 14]O[sub 25] (S[sub 4]A[sub 7]) is favored. The latter compound, whose composition is close to that of SA[sub 2], is stable up to 1500°C. At higher temperature it decomposes into SA and SA[sub 2], which in its turn decomposes into SA and SA[sub 6] (SrAl[sub 12]O[sub 19]). There is again another stability domain for SA[sub 2], restricted to a narrow temperature scale close to its melting point (∼1800°C). The behaviors at crystallization from amorphous precursors at low temperature and from liquid at very high temperature are symmetrical: low heating or cooling rates produce pure SA[sub 2] while too rapid kinetics result in mixtures of phases.
- Subjects
ALUMINATES; STRONTIUM compounds; CRYSTALLIZATION
- Publication
Journal of the American Ceramic Society, 2002, Vol 85, Issue 12, p3036
- ISSN
0002-7820
- Publication type
Article
- DOI
10.1111/j.1151-2916.2002.tb00575.x