High-Pressure Electrical Behavior and Equation of State of Magnesium Oxide from Shock Wave Measurements

Abstract

A decrease in resistivity of MgO from >10⁵ to ∼10³ 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 10³⁹ 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.