ELECTRON BACKSCATTER DIFFRACTION: RECENT ADVANCES IN OFFLINE INDEXING METHODS AND WHAT IT MEANS FOR GEOLOGICAL MATERIALS

Most recent advances for Electron Backscatter Diffraction (EBSD) focus on indexing speeds, with current systems seeing up to 7000 indexed points per second. These speeds are typically seen on high symmetry, highly conductive materials like steels and other alloys. While some of these speed advances are seen in geological materials, the lower symmetry, lower conductivity, and range of chemistries in a phase can cause issues in indexing.

Traditional indexing techniques focus on the Hough Transform, which reduces the EBSD pattern to a series of lines and the geometries between them. These lines are then compared to a database to give the phase and crystal orientation for each data point. This method reduces the full-frame patterns, ignoring other diffraction bands not detected by the Hough transform, high-level diffraction phenomena, and other helpful information.

In recent years, a new method of indexing has allowed researchers to understand their samples in new ways. This method, Spherical Indexing, combines a forward modeling approach with high-quality pattern simulations. Since this method uses the entire pattern, it allows the complete information of the pattern to be considered. Smaller changes that Hough-based approaches would ignore can now be studied and used to understand geological materials better. Recent studies on cation ordering, phase differentiation, and pseudosymmetry will be presented.