High-pressure phase transition of mullite under shock compression

Hugoniot measurements have been performed on mullite polycrystals in the pressure range up to 80 GPa by using a two-stage light-gas gun and a Doppler laser interferometer. The Hugoniot elastic limit is determined to be 16.1+/-2.2 GPa. The Hugoniot data show that the phase transition occurs at 30.4+/-3.6 GPa. Comparison of the Hugoniot data with calculated theoretical Hugoniots suggests that the high-pressure phase transition of mullite is its disproportionation to corundum and stishovite. The mixed phase region is between 30 and 70 GPa. It is indicated that this phase transition is very sluggish. (C) 2004 American Institute of Physics.