Electrical measurements on fused quartz under shock compression

The resistivities of specimens ofSi02 (fused quartz) singly and doubly shocked in the 10-45 and 27-90 GPa ranges, respectively, demonstrate a marked decrease from values of10-0.1 11-m at a single-shock pressure of -40 and a double-shock pressure of 7 4 G Pa. These states correspond to calculated shock temperatures of3300 and -3600 K, respectively. At shock pressures below 36 GPa the measured resistivity versus calculated shock temperature agrees closely with ambientpressure and high-temperature resistivity data. This suggests that the ionic conduction mechanisms inferred to control electrical properties at ambient pressure also act under shockinduced high temperatures in quartz and the presumed high-pressure phase, stishovite into which fused quartz appears to transform above 20 GPa. At 36-40 GPa the rapid decrease in resistivity by a factor of 10 suggests a further transformation to an unknown phase which may correspond to the onset of melting. The existing pressure-density Hugoniot data do not demonstrate any anomalous density change associated with this phase change.