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The Role of TiN in the Intergranular Phase‐Forming Process in TiN‐Dispersed Si 3 N 4 Nanocomposites
Author(s) -
Schmid Herbert K.
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.1551-2916.2005.00054.x
Subject(s) - intergranular corrosion , tin , materials science , grain boundary , dopant , phase (matter) , transmission electron microscopy , metallurgy , analytical chemistry (journal) , microstructure , nanotechnology , doping , chemistry , optoelectronics , organic chemistry , chromatography
Internal interfaces in two ceramic systems, monolithic Si 3 N 4 (SN) and TiN‐dispersed Si 3 N 4 nanocomposite (STN), were characterized by analytical transmission electron microscopy (TEM). In monolithic SN both MgO and Y 2 O 3 dopants are preferentially hosted by the vitreous intergranular phase in pockets at triple grain junctions (TJ), whereas in STN composites the highest dopant concentrations were observed in grain and phase boundaries. The width of grain boundary films, as revealed by high‐resolution TEM imaging, varied between ≈0.8 nm in monolithic SN and ≈1.0–1.2 nm in STN. Intergranular films with increased width ≈1.8 nm were detected in SN–TiN phase boundaries. Although no enrichment of Ti could be detected in the intergranular phase, it appears that the presence of TiN dispersants indirectly contributes to the intergranular phase formation. It is assumed that TiO 2 impurities sitting on TiN particle surfaces react with the matrix phase, resulting in a more oxidic nature of intergranular films due to increased SiO 2 supply in intergranular regions. Phase‐specific Si‐L 2,3 energy‐loss near edge structure features, which could serve as fingerprints for phase identification, were observed in spatial‐difference electron energy‐loss spectra from grain boundary films and TJ pockets.