High-pressure electrical behavior and equation of state of magnesium oxide from shock wave measurements

Abstract

A decrease in resistivity of MgO from >10^(5) to ~10^(3)Ω·cm is observed when thin single crystals are shocked in the [001] direction to 920±70 kbar. This effect may be produced by several electronic processes, or by ionic transport in which the effective O= or Mg++ diffusion constants are increased by perhaps a factor of 10^39 from those calculated at high pressure (according to Zener strain-energy model). Voltages are observed during passage of various-strength (70 to 936 kbar) shock fronts through the specimen. These voltages approximately scale as the inverse of the specimen thickness and may arise from net volume polarization (~0.2 to ~9 V/cm). Some Hugoniot data to 660 kbar (including measurement of elastic-shock amplitude varying from 35 to 89 kbar) are presented.