Direct observation of amorphous to amorphous apparently first-order phase transition in fused quartz - art. no. 195501

We report for the first time the direct observation of an apparently first- order phase transition in amorphous silica from the low density amorphous p hase to the high density amorphous phase with a discontinuous volume change of about 20% from the dilatometric measurements using the piston cylinder apparatus at 36 kbar and 680 degreesC. Our Raman spectroscopy measurements on the retrieved samples quenched from high pressure and high temperature e xperiments do not show any Raman peaks indicating a large modification in t he intermediate range order in the structure of amorphous silica.