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Formation of α‐Al 2 O 3 by thermal decomposition of basic aluminium chlorides at low temperatures
Author(s) -
Brand P.,
Troschke R.,
Weigelt H.
Publication year - 1989
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.2170240706
Subject(s) - corundum , amorphous solid , thermal decomposition , decomposition , aluminium , chemistry , salt (chemistry) , chloride , inorganic chemistry , aluminium chloride , transition metal , mineralogy , chemical engineering , materials science , crystallography , catalysis , organic chemistry , engineering
Basic aluminium chloride gels and the crystalline salt AlCl 3 · 2 Al(OH) 3 · 6 H 2 O are thermally decomposed to an amorphous product in a first step at low temperatures. If the reaction gas is rapidly removed the amorphous decomposition product directly transforms to corundum at increased temperature. Starting from gels the α‐Al 2 O 3 formation begins at 420 °C, transformation of the crystalline salt at 530 °C. Structural similarities of precursor compounds and corundum are discussed as a reason for this behaviour. High contents of HCl and H 2 O in the atmosphere surrounding the specimen result in decomposition to transition aluminas at increasing temperature, which are transformed into α‐Al 2 O 3 above 1000 °C.