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The externally heated diamond anvil cell (EHDAC) conducts high pressure and temperature experiments with spatial uniformity and temporal stability. These are conventionally combined with various spectroscopies and x-ray diffraction measurements. EHDAC techniques perform Joule heating on a heater placed close to or directly in contact with diamond anvils. However, the electrical wiring and heater required for Joule heating complicate EHDAC setups, hindering easy access for the measurement of physical properties. This study proposes an EHDAC technique using laser- instead of Joule-heating. We successfully achieved temperatures reaching 900 K by applying heat to diamond anvils through laser-heating of the gaskets with thermally insulating anvil seats. To test this setup, we measured the melting temperature of H2O ice VII, which was consistent with previous studies. We also measured the high-pressure and temperature impedance of H2O VII and verified the capability of electrical resistivity measurements in this setup. This technique allows various physical property measurements owing to its simple setup required for externally laser-heated diamond anvil cell experiments. The unique characteristics of this heating technique are that (1) no heaters or wiring are required, (2) it exhibits the most efficient heating among EHDAC studies, (3) it maintains the DAC body at room temperature, and (4) diamond anvils do not detach from anvil seats after the EHDAC experiment. This method significantly simplifies the experimental setup, which allows much easier access to various physical property measurements using an EHDAC.

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.

Semiconductor-based heaters for diamond anvil cells (DACs) have advantages over metal wire heaters in terms of repeated use and the ability to reach higher temperatures. We introduce a cylindrical SiC heater for an externally heated DAC (EHDAC) that works satisfactorily at temperatures up to 1500 K and pressures around 90 GPa. The heater is reusable and inexpensive, and only slight modifications to the DAC are required to fit the heater. Experiments on melting of NaCl and gold are conducted at ambient pressure to test the temperature accuracy of the EHDAC system, and resistance measurements on iodine at high pressures and temperatures are performed to assess the heater assembly. These test runs show that a uniform and accurate temperature can be maintained by the EHDAC assembly, which has potential applications to a variety of transport property measurements.