513 29
texture of the samples and an understanding of the fine
details present in the microstructure were extremely useful
in determining the cooling history and the microstructural
development in this meteorite. It should also not be lost on
the reader that EBSD and the related TKD span a huge range
of length scales from collecting large mm sized regions to
using extremely small step sizes to elucidate the nm scalede-
tails of the microstructure.
29.2.11 Summary
EBSD and the related technique of TKD are an important
part of crystalline materials characterization in the SEM. With
EBSD the SEM can now be considered a complete materials
characterization tool that can not only take excellent quality
images of samples but can determine the elemental constitu-
ents of the sample as well as the detailed crystallography.
29.2.12 Electron Backscatter Diffraction
Checklist
Specimen Considerations
EBSD requires a properly prepared sample that is securely
attached to an appropriate support as the sample will be tilted
to high angles to facilitate EBSD pattern acquisition. The
sample surface should be free of artifacts due to sample prep-
aration. Due to the high sample tilt and the generally long
acquisition times required for EBSD, carbon tape is not a
good choice as it tends to creep allowing the sample to move
causing drift related image issues. Samples mounted in epoxy
metallographic mounting materials are subject to drift caused
by charging of the polymer material. It is satisfactory to
lightly conductively coat the specimen for EBSD analysis
provided the coating is kept as thin as possible while remain-
ing adequate for charge removal.
Non-conductive samples may also be lightly coated for
analysis as discussed above. It is also possible to utilize the
variable pressure mode of operation to reduce charging
related artifacts. One must carefully choose the correct pres-
sure to be used as too high of a pressure will result in blurred
patterns due to scattering in the gas and too low of a pressure
may not control the charging.
Proper positioning of the specimen within the SEM is criti-
cal. One must remember that the sample will be tilted to a high
angle for analysis. The high tilt required for EBSD will limit
how tall the sample is and how it must be mounted on the SEM
sample stage. A sample that is too short may also present dif-
ficulties in positioning the sample in the proper location.EBSD Detector
Due to the limited space in most SEM sample chambers, it
is best to position the sample so that the sample is tilted
appropriately and the area to be analyzed is in the field of
view. Once the sample position has been established the
EBSD detector should be introduced. The exact location of
the detector is not extremely important, but the sample to
detector distance should be sufficiently short so that a large
solid angle can be obtained and the brightest part of the pat-
tern located in the upper half of the detector image. It is
very important to keep in mind the position of the sample
and the detector as there are two kinds of people who use
EBSD: Those who have hit the EBSD detector and those
who will. So be careful when moving the sample and the
detector. A chamberscope is absolutely required for safe
EBSD operation.ab. Fig. 29.27 TKD phase and orientation maps acquired from the thin
sample shown in. Fig. 29.18. The data was acquired at a beam volt-
age of 30 kV with a step size of 4 nm. This data was collected using an
on-axis TKD detector, as shown in. Fig. 29.13a. a Map with austenite
colored red and ferrite green. b Orientation map of both the austenite
and ferrite phases. Note the fine-scale twinning that occurs in the aus-
tenite precipitates29.2 · Electron Backscatter Diffraction in the Scanning Electron Microscope