We have investigated the effect of high-pressure on the crystallization of an Li2O-Al2O3-SiO2 glass. The glass was heated for nucleation, followed by heating for crystal growth. Hydrostatic pressure of argon gas of 196 MPa was applied in either the nucleation process or the crystal growth process, and in both the processes. β-quartz solid solution was precipitated in all glass-ceramic specimens. The crystallinity of the glass-ceramics increased by applying high-pressure during the nucleation or the crystal growth process. Lattice constants of the precipitated crystal were decreased by applying high-pressure. Magnitudes of the increase of crystallinity and the decrease of lattice constants by applying pressure in the crystal growth process were larger than these in the nucleation process. Density of glass-ceramic specimens increased by applying pressure in any heat treatment. It was suggested that the increase in density is due to increase of crystallinity, decrease of lattice constant and possibly densification of glass part. The refractive index increased with increasing density. The temperature coefficient of the optical path length, dS/dT, decreased by applying pressure.
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