Need to do EBSD?
Discover new dimensions with EBSD analysis tailored to your research goals.
EBSD analysis
Explore crystallographic structure of your material
Understanding EBSD
Electron Backscatter Diffraction (EBSD) occurs when a source of accelerated electrons, such as the electron beam in a Scanning Electron Microscope (SEM), hits the crystalline structure of a target material.
Typically, the interaction of an incoming electron beam with a solid material causes ionisation and scattering of electrons – some of which are backscattered out of the material. Part of these backscattered electrons are deflected (i.e. diffracted) by the crystalline structure of the material, following Bragg’s law of diffraction.
Only the electrons that satisfy Bragg’s law will escape the material, creating cone-like geometries (Laue diffraction cones) that are unique to the crystallographic plane of diffraction that made them. In the SEM, these cones are captured by a phosphor screen, producing what the EBSD community knows as Kikuchi patterns. The Kikuchi patterns are a fingerprint of the spatial arrangement of the crystallographic lattice planes of the material being analysed.
Potential of EBSD
You can use EBSD to measure the 3D crystallographic orientation of the mineral grains in a specimen. It allows you to better understand the material’s microstructure and physical properties, which often relate to the orientation, dimension and internal lattice misorientations of the mineral grains that make up the material. With EBSD, you can analyse the preferential growth direction of metals, ceramics, natural rock minerals, or subsequent changes in the crystal’s orientations caused by stress regimes.
Only the electrons that satisfy Bragg’s law will escape the material, creating cone-like geometries (Laue diffraction cones) that are unique to the crystallographic plane of diffraction that made them. In the SEM, these cones are captured by a phosphor screen, producing what the EBSD community knows as Kikuchi patterns. The Kikuchi patterns are a fingerprint of the spatial arrangement of the crystallographic lattice planes of the material being analysed.
You can use EBSD to measure the 3D crystallographic orientation of the mineral grains in a specimen. It allows you to better understand the material’s microstructure and physical properties, which often relate to the orientation, dimension and internal lattice misorientations of the mineral grains that make up the material. With EBSD, you can analyse the preferential growth direction of metals, ceramics, natural rock minerals, or subsequent changes in the crystal’s orientations caused by stress regimes.
Sample suitability for EBSD
Not all samples can be analysed with EBSD. Only samples that are crystalline, extremely flat and polished, can be analysed. If you have a sample that is amorphous, such as glass, it cannot be analysed with EBSD as there are no crystallographic lattices to diffract electrons from.
You can only analyse what sits on the surface of your sample, the technique does not penetrate the material.
You can send us your sample already polished, but we also offer in-house polishing using alumina paste, diamond paste or colloidal silica.
We will need to understand your material first before we perform EBSD – i.e. its mineralogy or crystal structure. This is because we have to pair it to its reference crystallographic structure that we have in our database.
Process overview
- Conductive samples require no additional steps.
- Non-conductive samples are coated with a thin layer of carbon before analysis.
- Sample is mounted on a holder in the SEM Zeiss Crossbeam 550 FIB-SEM equipped with our Oxford Instruments EBSD detector.
- SEM beam rasterizes the sample, creating EBSD maps of crystallographic orientations.
- 2D EBSD maps provide insights into grain/mineral orientations.
Expected EBSD data
You’ll receive a comprehensive report including electron images, selected EBSD maps, and the raw data file. Elemental chemistry maps (EDS) can be included upon prior request. EBSD raw data is a table of crystallographic orientations that can be processed for orientation distributions, grain sizes, and misorientations.
EBSD Limitations
- Requires a polished surface with less than 1µm polishing grade.
- Knowledge of the target mineral for crystallographic data.
- Time-consuming; one sample per session.
- Acquisition time varies (3-12 hours per map) based on area and step size.
- Post-processing expertise is necessary.
FAQs
How much does it cost?
The cost depends on the acquisition time, which in turn depends on the quality and quantity of output that you are after. Cost is £220 per hour.
How many samples can I analyse with EBSD in one session?
Typically just one, but you may do more than one area of interest in the sample.
What is the spatial resolution?
Ultimately what determines the resolution in the EBSD maps is the step size (or pixel size). A large map (e.g. 1000 µm across) may require a step size of 10 µm so any feature smaller than 10 µm cannot be resolved. However, the beam of the SEM can resolve sub-micron features easily, so it is possible to acquire features with 0.2-0.3 µm step size.
What is the angular resolution?
A safe threshold is 2 degrees, but typically 0.5 degrees or less can be achieved.
What materials can I measure?
Any crystalline material that we have in our inorganic crystal structure database, or any crystalline material you have the lattice unit cell parameters and Laue crystal classes that we can input.
I have a material that contains more than one mineral type. How many minerals can I measure in the same session?
As long as the minerals are in the structural database, then you may add as many as you need to the acquisition. It is however advised to stick to less than 5 minerals as the automatic indexing may swap one mineral for another if the crystallographic patterns of the two minerals are similar enough.
My results are poor: poor indexing (recognition) of patterns so that image looks pixelated, or streaks across the EBSD map – why?
As much as we strive for delivering excellent results, sometimes things don’t go as planned. Poor indexing can be due to one of the following: poor sample preparation; difficult crystal symmetries (triclinic or monoclinic being the most challenging) which causes failure in Kikuchi pattern recognition; errors in pattern recognition due to similar or undistinguishable patterns; inadequate setup geometries. Sometimes the materials are beam sensitive and the crystal lattice degrades over time under the beam (e.g. apatite). Therefore, in some unlucky cases the beam destroys the lattice and thus fails to give diffraction patterns. Streaks across the EBSD map could be due to charging of the sample, or creeping of the tilted sample in the chamber, although such problems can be generally avoided.
How long does it take?
We aim to provide you with the requested EBSD results between 2 to 4 weeks. Please contact us to discuss and find out more. Each EBSD run typically takes no less than 2 hours of acquisition time + 1 hour setup. However, longer sessions are not uncommon. The time take to acquire EBSD maps depends on the size of the area to be mapped, the required step size (i.e. map resolution) and on the dwell time (i.e. acquisition speed). It is therefore always a trade-off between the parameters that suit your research needs, time and costs.
