High-P–T impedance measurements using a laser-heated diamond anvil cell

Abstract

The electrical conductivity (EC) of minerals found on Earth and throughout the solar system is a fundamental transport property that is used to understand various dynamical phenomena in planetary interiors. High-pressure and high-temperature ( P–T) EC measurements are also an important tool for observing phase transitions. Impedance measurements can accurately measure the EC of a nonmetallic sample. In previous measurements under static conditions using a laser-heated diamond-anvil cell (LHDAC), only direct current resistance is measured, but this method overestimates the bulk sample resistance. Moreover, the previous methodology could only be applied to nontransparent samples in an LHDAC using infrared lasers, limiting the range of measurable composition. To the best of our knowledge, no in situ high- P–T EC measurements of transparent materials have been reported using LHDAC techniques. We developed a novel impedance measurement technique under high- P–T conditions in an LHDAC that applies to transparent samples. As a validation, we measured the EC of Mg0.9Fe0.1SiO3 bridgmanite up to 51 GPa and 2000 K and found that the results are consistent with those of previous studies. We also measured the EC values of sodium chloride to compare with those of previous studies, as well as those of cubic boron nitride and zirconia cement to quantify how well they insulate under high P–T conditions. This is the first report of the impedance and EC measurements of transparent minerals in an LHDAC, which allows the measurement of Fe-poor/-free materials, including the major constituents of the interiors of gas giants and icy planets, under extreme conditions.

In Situ Measurement Techniques Using Diamond Anvil Cell at High Pressure–Temperature Conditions: A Review

“…Okuda et al [55] tested the in situ resistivity of NaCl under the condition of an LH-DAC and found that the resistance tended to [41] Copyright 2019, APS.…”

“…Okuda et al [ 55 ] tested the in situ resistivity of NaCl under the condition of an LH‐DAC and found that the resistance tended to decrease with an increase in temperature at 21 and 33 GPa, as shown in Figure a and b. Hong et al [ 56 ] investigated the structural and electrical transport properties of natural barite under the conditions of 298–873 K and 1.5–35 GPa using a DAC through electrical conductivity measurements.…”

“…Reproduced with permission. [ 55 ] Copyright 2022, AIP Publishing. c) Variation of the conductivity of natural barite at a 11.5 GPa and 298–873 K. Reproduced with permission.…”

Electrical Conductivity of Dense MgSiO3 Melt Under Static Compression

“…Here we measured the EC of molten dense MgSiO 3 , representing the chemical composition of terrestrial magma ocean, at 39–71 GPa and 3460–4490 K by a pseudo‐four‐probe direct current resistance measurement and a recently‐developed cell configuration capable of measuring the conductivity of transparent materials in a laser‐heated diamond‐anvil cell (DAC) (Okuda et al., 2022).…”