[S-CG50] Rheology, fracture and friction in Earth and planetary sciences

[SCG50-09] Electron diffraction imaging to analyze local deformations in Earth and planetary materials

★Invited Papers

*Yohei Igami¹, Akira Miyake¹ (1.Graduate School of Science, Kyoto University)

Keywords:electron microscopy, electron diffraction, local deformation, crystal preferred orientation

It remains challenging in mineralogy to reveal micro/nanometric heterogeneity of crystal structure and the relevant properties within naturally occurring minerals. Electron microscopy is acknowledged to be effective to tackle the issue. Recently developed scanning transmission electron microscopy (STEM) provides extremely high spatial resolution to directly visualize atomic arrangement of crystalline materials, but the field of view is too limited to grasp their nanometer/micrometer-scale heterogeneity. Thus, we focus on an alternative method which uses an electron nanoprobe to record many two-dimensional (2D) diffraction patterns over a 2D grid of probe positions from nanometer/micrometer regions. This approach (diffraction imaging, 4D-STEM [1]) is able to evaluate crystal structural parameters at each probe position with a clear STEM image. In the presentation, we will introduce our mineralogical and Earth/planetary scientific applications of the technique.
If unexpected local-deformation process exists in some Earth/planetary material, it may crucially affect the bulk mechanical properties in various situations. The diffraction imaging technique would be effective also to solve the problem, because this technique enables us to evaluate lattice strain, crystal preferred orientation and dislocation property within the samples having complex mineralogical/petrological textures.

Reference
[1] Ophus, C. (2019) Microsc. Microanal. 25, 563.