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A New Investigation of the Cl − –CO 3 2− Substitution in AFm Phases
Author(s) -
Mesbah Adel,
CauditCoumes Céline,
Frizon Fabien,
Leroux Fabrice,
Ravaux Johann,
Renaudin Guillaume
Publication year - 2011
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.1551-2916.2010.04305.x
Subject(s) - monoclinic crystal system , crystallography , solid solution , raman spectroscopy , chemistry , carbonate , crystal structure , organic chemistry , physics , optics
Chloride to carbonate substitution in AFm phase of general formulae [Ca 2 Al(OH) 6 ]·[Cl 1− x ·(CO 3 ) x /2 ·(2+ x /2)H 2 O] (or 3CaO·Al 2 O 3 ·(CaCl 2 ) 1− x ·(CaCO 3 ) x ·(10+ x )H 2 O written in cement notation) has been characterized by studying 12 powdered samples synthesized at 25° and at 85°C. The existence of a solid solution has been highlighted. It forms one stable rhombohedral [Ca 2 Al(OH) 6 ]·[Cl 1− x ·(CO 3 ) x /2 ·(2+ x /2)H 2 O] solid solution with 0.25≤ x ≤0.95, isotypic with the recently describedchloro‐carboaluminate of [Ca 2 Al(OH) 6 ]·[Cl 0.5 ·(CO 3 ) 0.25 · 2.25H 2 O] composition. A second metastable monoclinic [Ca 2 Al(OH) 6 ]·[Cl 1− x ·(CO 3 ) x /2 ·(2+ x /2)H 2 O] solid solution has also been identified in a less extended x domain. The structural relationship between these two stable and metastable chloro‐carboaluminate polymorphs shows similarities with the structural transition of the Friedel's salt (from rhombohedral high‐temperature‐structure to monoclinic low‐temperature‐structure at about 35°C). The two [Ca 2 Al(OH) 6 ]· [Cl 1− x ·(CO 3 ) x /2 ·(2+ x /2)H 2 O] solid solutions are simultaneously present, in quite equivalent weight amounts, in samples synthesized at room temperature, whereas only the stable rhombohedral polymorph is observed for samples synthesized at 85°C. Raman spectroscopy has been successfully used to locate carbonate in the structure. The [CO 3 ] symmetric stretching mode is observed at 1068 cm −1 for monocarboaluminate ( x =1) for carbonate directly bonded to main layer, while it is observed at 1086 cm −1 for both chloro‐carboaluminate polymorphs, which is characteristic of interlayer carbonate.