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Relationship Between Structure and Glass Transition Temperature in Low‐silica Calcium Aluminosilicate Glasses: the Origin of the Anomaly at Low Silica Content
Author(s) -
Cormier Laurent,
Neuville Daniel R.,
Calas Georges
Publication year - 2005
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.1551-2916.2005.00428.x
Subject(s) - aluminosilicate , depolymerization , glass transition , neutron diffraction , materials science , octahedron , calcium aluminosilicate , diffraction , crystallography , mineralogy , content (measure theory) , analytical chemistry (journal) , chemistry , crystal structure , optics , mathematical analysis , biochemistry , polymer , physics , mathematics , chromatography , polymer chemistry , composite material , catalysis
The anomalous behavior of the glass transition temperature ( T g ) in low silica calcium aluminosilicate glasses has been related to the structural modifications observed by neutron and X‐ray diffraction. The diffraction data indicate that Al and Si are in tetrahedral sites and that Ca atoms are in distorted octahedral sites. By subtracting the correlation functions for glasses at constant SiO 2 or constant Al 2 O 3 content, we have shown that Si and Al atoms are introduced in a different way within the glass structure. Si is present in various Q n sites, while Al resides in Q 3 and Q 4 sites for glasses with high CaO content and enters fully polymerized Q 4 sites with increasing SiO 2 or Al 2 O 3 content. The higher proportion of Al in Q 3 positions at high CaO content yields a depolymerization of the network. The lower connectivity will contribute to a decrease of the viscosity, which may be at the origin of the decrease of T g for glasses at low silica content.