A Raman spectroscopic study of shock-wave densification of anorthite (CaAl2Si2O8) glass

Structural modifications induced by shockwave compression up to 40 GPa in a northite glass are investigated by Raman spectroscopy. In the first investi gation, densification increases with increasing shock pressure, A maximum d ensification of 2.2% is obtained for a shock pressure of 24 GPa. This densi fication is attributed to a decrease of the average ring size, favoring thr ee-membered rings. The densification is much lower than in silica glass sub ject to shock at similar pressures (11%). because the T-O-T bond angle decr ease is impeded in anorthite glass. For higher shock pressures, the decreas e of the recovered densification is attributed to partial annealing of the samples due to high after-shock residual temperatures. The study of the ann ealing: process of the most densified glass by in-situ high temperature Ram an spectroscopy confirms that relaxation of the three-membered rings occurs above about 900 K.