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Solubility of Si 3 N 4 in Liquid SiO 2
Author(s) -
Gu Hui,
Can Rowland M.,
Seifert Hans J.,
Hoffmann Michael J.,
Tanaka Isao
Publication year - 2002
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.1151-2916.2002.tb00033.x
Subject(s) - solubility , metastability , silicate , phase diagram , amorphous solid , mixing (physics) , enthalpy of mixing , phase (matter) , enthalpy , dissolution , ion , materials science , analytical chemistry (journal) , liquid nitrogen , crystallography , chemistry , thermodynamics , organic chemistry , physics , quantum mechanics
The nitrogen solubility in the SiO 2 ‐rich liquid in the metastable binary SiO 2 ‐Si 3 N 4 system has been determined by analytical TEM to be 1%–4% of N/(O + N) at 1973–2223 K. Analysis of the near edge structure of the electron energy loss peak indicates that nitrogen is incorporated into the silicate network rather than being present as molecular N 2 . A regular solution model with a positive enthalpy of mixing for the liquid was used to match the data for the metastable solubility of N in the presence of crystalline Si 3 N 4 and to adjust the computed phase diagram. The solubility of Si 3 N 4 in fused SiO 2 is far less than reported in liquid silicates also containing Al, Mg, and/or Y. Apparently, these cations act as modifiers that break anion bridges in the silicate network and, thereby, allow further incorporation of Si 3 N 4 without prohibitive amounts of network cross‐linking. Finally, indications emerged regarding the diffuse nature of the Si 3 N 4 ‐SiO 2 interface that leads to amorphous regions of higher N content.