Recent features in EBSD, including new trapezoidal correction for multi-mapping

Abstract

EBSD (electron backscatter diffraction) of geological samples can be a challenge due to the complex crystal structures of minerals and commonly 5 or more different minerals in the samples. This poses a big challenge as the EBSP (electron backscatter diffraction patterns) of the minerals like feldspar and quartz commonly are much noisier than metallurgical materials that have simpler structures. Therefore, the indexing of geological samples can commonly be quite difficult and to correct for this in the online procedure means that the data acquisition needs to be redone on the SEM. This is a costly procedure, also because the indexing can take longer than the pattern acquisition itself. We, therefore, suggest that offline techniques are better suited for geological materials because the patterns can be re-indexed using different settings and further can be processed using different software both for indexing and pattern improvement. EBSD commonly have geometric scan distortion which increases with decreasing magnification. This problem is solved by acquiring using a geometric online scan correction during data collection in the NORDIF software using calibration grid. This overcomes stitching problems and additionally removes hidden problems such as geometrically distorted grain boundary segments and grain shape distortions.

Deformation Mechanisms of Blueschist Facies Continental Metasediments May Offer Insights Into Deep Episodic Tremor and Slow Slip Events

“…The Matlab toolbox MTEX (Bachmann et al, 2010(Bachmann et al, , 2011Mainprice et al, 2015) was used to process the data. Noise reduction was conducted to filter mis-indexed points and artifacts according to procedures described by Sørensen et al (2020). High-angle grain boundaries were traced for a misorientation >10° whereas low-angle boundaries for misorientations in the 2-10° interval.…”

Syn‐Orogenic Exhumation of High‐P Units by Upward Extrusion in an Accretionary Wedge: Insights From the Eastern Elba Nappe Stack (Northern Apennines, Italy)

“…Noise reduction was performed to eliminate mis-indexed points and artifacts. During indexing, grain boundaries between calcite grains are often misinterpreted as dolomite (Sørensen et al, 2020). Therefore, we removed false dolomite grains.…”

“…Samples were mounted on metal mounting pedestals, at the standard eccentric height, using a tilt angle of 70° with respect to the horizontal (Prior et al, 2009) and a working distance of 21.9 mm. To avoid geometric trapezoidal scan distortions in the collected maps, a correction to the beam scan voltages was implemented using a gridded standard calibration (Sørensen et al, 2020). To acquire optimal EBSD patterns, the SEM vacuum was set on a variable pressure mode, low vacuum setting, and an accelerating voltage of 20 keV, using an extraction voltage of 1.70 kV and open apertures.…”

Hysteresis parameters and magnetic anisotropy of silicate-hosted magnetite exsolutions

“…The samples were mounted on metal pedestals at standard eucentric height with a tilt angle of 70 • and working distance of 22.0 mm. To avoid geometric trapezoidal scan distortions in the maps, a beam scan voltage correction was implemented using a EM-Tec LAMC-15 large area magnification calibration standard [Sørensen et al, 2020]. EBSD patterns were acquired using a NORDIF UF-1000 detector and the NORDIF 3.0 software.…”

“…Indexing was done using the TSL-OIM 7.2 software at the Department of Material Science and Engineering, NTNU. EBSD data cleanup was done according to the procedures described in Sørensen et al [2020], checking the consistency of indexing and cleanup procedures.…”