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Occurrence of Pseudotetragonal Mullite
Author(s) -
Schneider Hartmut,
RymonLipinski Tadeusz
Publication year - 1988
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.1151-2916.1988.tb05042.x
Subject(s) - mullite , orthorhombic crystal system , tetragonal crystal system , phase (matter) , crystallography , materials science , crystal twinning , mineralogy , chemistry , crystal structure , metallurgy , microstructure , ceramic , organic chemistry
Mullite‐type phases with about 74 wt% Al 2 O 3 and 26 wt% SiO 2 were prepared from tetraethyl orthosilicate and aluminum butylate between 950° and 1000°C. The lack of 120/210, 240/420, 041/401, and 250/520 reflection pair splitting on the X‐ray diffractograms indicates tetragonal symmetry, whereas normal mullite is orthorhombic. We believe that the tetragonal character of the phase is due to twinning and/or domain formation of orthorhombic structural units in an elementary cell scale. Therefore, the mullite‐type phase should be designated as pseudotetragonal rather than tetragonal. According to our present knowledge, pseudotetragonal mullite is formed from highly reactive metal organic compounds only. The phase is metastable and transforms gradually to orthorhombic mullite at temperatures above 1000°C.