Pressure-induced enhancement of proton conduction in brucite

The electrical conductivity of single-crystal brucite was measured as a function of pressure and temperature (P-T) using impedance spectroscopy (IS). IS measurements demonstrated that electrical conductivity perpendicular to the c axis is nearly half order of magnitude higher than that parallel to the c axis under the same P-T conditions. Electrical conductivity increased by 2 orders of magnitude during compression from 3.7 to 11 GPa, irrespective of crystallographic direction. However, the conductivity increase with pressure became less significant upon further compression from 11 to 13 GPa. The pressure effect is closely related to the interactions between neighboring hydroxyls. The ratio of free protons to total hydrogen increases from 2% to 33% when pressure increases from 3.7 to 13 GPa at 950 K. This indicates that most of the protons are bound within the crystal structure at low pressures, whereas more protons become free and mobile at higher pressures. Key Points Electrical conductivity of brucite is measured under high P-T conditions Electrical conductivity of brucite is greatly enhanced by compression More protons become mobile at higher pressure