Thermal expansion of vitreous silica: Correspondence between dilatation curve and phase transitions in crystalline silica

The linear thermal expansion coefficients of fused quartz containing 3 ppm of OH produced by electrical melting of natural quartz powder were measured using an interferometric dilatometer in the temperature range 300-970 K. The data obtained show several maxima and minima, some of which correspond to the phase transitions in crystalline silica. A sharp maximum is observed at 500 K, which corresponds to the alpha to beta transition temperature of cristobalite. Minima at 850 and 580 K correspond to low-to high-temperature phase transitions of crystalline quartz and tridymite, respectively. This correspondence was not observed in synthetic fused silica containing about 800 ppm of OH. (C) 1997 American Institute of Physics.