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Solid Solution Range and Microstructures of Melt‐Grown Mullite
Author(s) -
KRIVEN W. M.,
PASK JOSEPH A.
Publication year - 1983
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1983.tb10615.x
Subject(s) - mullite , microstructure , materials science , superstructure , plagioclase , solid solution , mineralogy , metastability , crystallography , phase (matter) , chemical composition , metallurgy , quartz , chemistry , thermodynamics , ceramic , physics , organic chemistry
The solid solution range of melt‐grown mullite was examined by crystal‐chemical methods. The maximum Al 2 O 3 content as determined by EDX was ∼83.6 wt%, 75 mol%, or the nominal composition 3Al 2 O 3 .SiO 2 . For samples of overall composition 81 to 83 wt% Al 2 O 3 , 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‐A1 2 O 3 , 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 SiO 2 ‐Al 2 O 3 metastable phase equilibria are discussed.