Electrical measurements on fused quartz under shock compression

The resistivities of specimens of SiO2 (fused quartz) singly and doubly shocked in the 10–45 and 27–90 GPa ranges, respectively, demonstrate a marked decrease from values of ∼10–0.1 Ω⋅m at a single-shock pressure of ∼40 and a double-shock pressure of ∼74 GPa. These states correspond to calculated shock temperatures of ∼3300 and ∼3600 K, respectively. At shock pressures below 36 GPa the measured resistivity versus calculated shock temperature agrees closely with ambient-pressure and high-temperature resistivity data. This suggests that the ionic conduction mechanisms inferred to control electrical properties at ambient pressure also act under shock-induced 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 102 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.