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Transmission Electron Microscopy and Electron Energy‐Loss Spectroscopy Characterization of Glass Phase in Sol‐Gel‐Derived Mullite
Author(s) -
Kleebe HansJoachim,
Hilz Gabriela,
Ziegler Günter
Publication year - 1996
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.1151-2916.1996.tb09021.x
Subject(s) - mullite , materials science , sintering , grain boundary , transmission electron microscopy , energy dispersive x ray spectroscopy , mineralogy , composite material , amorphous solid , microstructure , scanning electron microscope , ceramic , crystallography , chemistry , nanotechnology
Sol‐gel‐derived mullite ceramics were processed by pressureless sintering at 1600°, 1650°, and 1700°C for 4 h. Microstructural and microchemical characterization of the mullite materials was performed using transmission electron microscopy, in conjunction with energy‐dispersive X‐ray spectroscopy and electron energy‐loss spectroscopy (EELS). Apart from mullite grain diameter and triplepocket size, no major microstructural changes were observed with increasing sintering temperature. Residual glass was present at triple pockets and along two‐grain junctions. Not all grain boundaries revealed the presence of a continuous amorphous intergranular film. Clean interfaces were observed only at boundaries with one grain parallel to the [001] orientation (low‐energy configuration). Quantitative EELS analysis of mullite grains and glass pockets revealed only small changes in composition with increasing sintering temperature; i.e., the alumina:silica ratio slightly increased for mullite and glass. The analysis implied that mullite with this relatively high aluminum content would not be stable adjacent to residual glass. However, a stable glass‐mullite system has been proposed, because impurity cations were detected within glass pockets, which suggested a slight shift of the subsolidus line (glass‐mullite/ mullite) to a higher amount of alumina. Energy‐loss nearedge structure studies of the Si‐ L 2,3 edge revealed a similar near‐edge structure for the mullite, residual glass, and quartz. Thus, SiO 4 tetrahedra were thought to be the main building units of the glass contained in sintered mullite.