[S-CG58] Innovation through the Integration of Solid Earth Science and Materials Science

[SCG58-04] In situ electrical conductivity measurements during large deformation experiments by combining a rotational diamond anvil cell with boron-doped diamond

★Invited Papers

*Shintaro Azuma¹, Ryo Matsumoto², Kenji Ohta¹, Yoshihiko Takano² (1.Tokyo Institute of Technology, 2.NIMS)

The recently developed rotational diamond anvil cell (rDAC) has enabled quantitative large strain deformation experiments at pressures corresponding to the lowermost mantle (Nomura et al., 2017; Azuma et al., 2017). Stable and homogenous high-temperature conditions on deformation sample have also been achieved by introducing a near-infrared focused heating system (Image furnace) to rDAC (Azuma et al., 2024). These rDAC and heating system have been optimized for BL47XU, SPring-8 and, in combination with high-brilliance X-rays, allow in-situ measurements of phase transformation, differential stress, and crystallographic preferred orientation (CPO) of samples during deformation (Park et al., 2022). This rDAC system is expected to contribute to our understanding of the deformation properties of lower mantle minerals. On the other hand, large strain deformation experiments under high-pressure and high temperature using rDAC are not only contributing to solid earth science, but also have potential applications in the field of materials science. As a first step, our research group has started to develop a combination of rDAC and boron-doped diamond (BDD) (Matsumoto et al., 2016) to enable in situ electrical conductivity measurements under ultrahigh pressure and large strain deformation. In our experiments, the rDAC achieves high pressure conditions by sandwiching the sample between pairs of diamond anvils, as well as conventional DAC. Additionally, torsional deformation is applied to the sample by rotating the upper anvil at a constant speed. On the other hand, the lower anvil remains stationary during the deformation experiments, and BDD is used for the lower anvil. Such high-pressure torsional testing is known as one of the Severe Plastic Deformation (SPD) in the field of materials science. For example, large-strain plastic deformation experiments have been conducted to change the mechanical properties of metals (e.g., Valiev et al., 2000). In addition, indirect bandgap semiconductors, such as silicon (Si) and germanium (Ge), are known to change their electrical conductivity by one order of magnitude or more when subjected to high-pressure, rapid pressure reduction, and annealing. Recently, research aimed at improving semiconductor performances by introducing grain refinement, metastable phases, and dislocations through torsional deformation has also been attracting attention (e.g., Ikoma 2019). Within these trends in materials science, the technical development of rDAC+BDD will enable the measurement of physical properties under previously unattainable extreme conditions and could be a breakthrough in the search for new materials and new properties. In this presentation, we will introduce the development status of rDAC+BDD, present preliminary experimental results, and discuss existing challenges with a view toward its application in materials science.