Abstract
Microstructure and grain growth were studied in two glass ceramics of the Li2O-Al2O3-SiO2 system, one an experimental material of basic composition Li2O-Al2O3-4SiO2 and the second a commercial material of approximately 0.7Li2O-Al2O3-6SiO2 composition with small amounts of other oxides. There was evidence from transmission electron microscopy that the commercial material contained residual glass at grain-boundary triple points and glass layers at some but not all grain boundaries. No definite evidence was found for residual glass in the experimental material. The composition of secondphase regions in the commercial material was studied by STEM microanalysis. Al-rich regions of irregular morphology were found but there was no evidence that residual glass was SiO2-rich, as has been previously suggested for this type of glass-ceramic. Grain growth showed a fairly similar time dependence in the two materials with growth more rapid in the commercial material at a given temperature. It is suggested that grain growth is controlled by precipitate particles rather than by residual glass phase.
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