Advances in Integrated EDS-EBSD Analysis

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Marilynn Bradley
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1 Advances in Integrated EDS-EBSD Analysis Q&A from EDAX/Materials Today webinar: October 24, QuestionText I am studying the effect of sintering conditions such as atmosphere, pressure on the grain growth abnormality in layered pervoskites. In TEM studies stacking faults are visible, and there occurrence were influenced by sintering pressure and atmosphere, I want to know precisely the fault density and the structure variation in that regions. I want to know whether EDS or EBSD can be useful to understand it?, if not could you please suggest me a technique which will be useful for the same. Thank you in advance Best Regards Nivas Babu Selvaraj Department of Materials and Ceramic Engineering/CICECO University of Aveiro, Campus Universitario de Santiago Aveiro, PORTUGAL I am doing the electrochemistry on the surface of polycrystalline platinum and want to correlate them to the surface structure. However, the EBSD images which I got for a same scanned area are not repeatable. After rotating the sample 90 degree,the colour was different As mentioned the chip plays a greater role that means every single machine may work differently and also they may vary in the amount of data collection so is there any universal tool of comparison or all depends on different machines? Answer Stacking faults are generally visibile at resolutions exceeding that which can be achieved in the SEM and thus TEM is generally the tool most suited for studying such phenomena. However, you might want to explore the ECCI work of Stefan Zaefferer and Ivan Gutierrez. EBSD is used to determine the orientation of the crystal in question and then the information derived from the orientation in order to position the sample in such a way that some of the fine deformation structure can be observed: I.Gutierrez-Urrutia, S. Zaefferer & D. Raabe (2013) "Coupling of Electron Channeling with EBSD: Toward the Quantitative Characterization of Deformation Structures in the SEM", JOM, 9, It may be possible to get some indication of the fault density through low-angle misorientations measured via EBSD. I would suggest our paper on the subject: Wright, S. I., M. M. Nowell and D. P. Field (2011). "A review of strain analysis using electron backscatter diffraction." Microscopy and Microanalysis 17(3): I assume you rotated 90 degrees about the sample normal. In this case, the color should be the same in an IPF map unless the IPF map is generated for a sample direction that is not parallel to the sample normal. If this is not the case, there must be something wrong in how your system is configured. We will have someone contact you off-line to make sure your system is configured correctly. If my memory is correct there were some interesting experiments done in this arena by Koenig and coworkers. This is the paper I recall reading: König, U. and B. Davepon (2001). "Microstructure of polycrystalline Ti and its microelectrochemical properties by means of electron-backscattering diffraction (EBSD)." Electrochimica Acta 47: One means of standardizing the amount of statistical data counts is to collect in "Live Seconds" versus clock seconds. Live seconds will account for counts lost to dead time and will collect longer to make up for those lost counts. Therefore, an analysis collected with live time as the basis will remove differences from fluctuations in dead time between analyses. A second means for standardizing the data is to collect until a certain number of counts is attained. For example, at 100K input CPS for 1 second, a spectrum will contain 100K counts total. Data collected at 10K CPS would have to collect for 10 seconds to reach the same amount of data. 5 proc. time = beam dwell time? Process time is the setting of the EDS pulse processing electronics. It is the amount of time that the amplifier allows the rise and fall, or shaping, of the electronic pulse. Longer processing times will collect more slowly, or have higher dead time, therefore it is desirable to have a shorter processing time so that maximum collection speeds are possible. As the process time speeds up, the resolution will degrade, so it is necessary to have both fast processing speeds and quality resolution. This is an inherent quality of the Octane electronics. 6 On Page 18, how does the software calculate the error percentage? The error value as reported on page 18 is calculated as the difference from the known value. (collected value - known value)/known value. In general, an EDS error value will be reported with a quantitative analysis and that reporting is a function of the peak to background (S/N) and other analytical factors such as background corrections and peak deconvolutions. 7 Why hexagonal OIM Scan The hexagonal grid is helpful for reconstructing grain boundaries from the OIM measurements. Just like in finite-element work mapping the microstructure with a hexagonal grid provides a bit better link to the physical reality. We put together an application note on this subject a few years ago that we will try to make available on the website.

2 I currently use the EDAX in my experiment to check the carbide phase (intermetallic phase). The phase is mainly contain Carbon and some metallic element such as Chrome, Moly, etc etc. Do you think is it a good enough method to use the EDAX as the main source of information to decide the composition of the carbide. I ask this because in many cases, I found the element quantity of carbon is much more than I expected? Is there a way to implement an in-line script such that it would automatically rescan any point that has poor reliability in order to try to improve the match confidence? 1. Do the Octane detectors have the ability to detect C, O, N? (i.e. ultra-thin window detectors.) Can they detect Boron? 2. What about quantification of these constituents? Has quantification with SDD's of these lighter elements improved over SiLi? We have always had issues quantifying these constituents in metals/metallic reaction products. Thank you for your question. The quantification of light elements with EDS is more difficult in part due to the high amount of absorption of the low energy x-ray from both the sample and the detection process. There are matrix correction factors in the analysis (RZAF) to increase the accuracy. However, often an approach using partial standards will increase the accuracy. The EDAX software allows standardless Element Correction factors (SECs) which can be performed to adjust the correction for these low energy elements. Based on your description, I believe the standardless correction factors are not fully characterizing your matrix effects. Therefore, if you use SECs to standardize your carbon concentrations with a known carbon standard from a similar matrix, you can then apply this factor to your samples and get a more favorable result. Currently, the software allows all the points to be rescanned if there are overall reliability problems in the EBSD scan data that need to be addressed. However, not individual points. However, individual points can be addressed through the OIM Analysis software with a wide variety of cleanup methods. Yes, the Octane SDDs can detect and quantify these elements. Please see the answer above. 11 In terms of producing grain boundary image how precise one has to focus the beam at different and how precisely one can tell that they are focusing the grain boundaries not the grain. Of course, one wants to always focus the beam as well as possible for these measurements. A well focused beam will result in a smaller interaction volume thus providing the best resolution. At high tilts, it can be difficult to observe the grain boundary structure using the standard secondary electron detector in the SEM or a backscatter detector. Thus, using a forward scatter detector can help identify grain boundaries in the microstructure before proceeding with a full mapping measurement. However, this is not always possible either. We will sometime run some coarse scans on the material to try and get a feel for a good magnification for the grain boundaries and then proceed. When the electron beam is on a grain boundary then the interaction volume is spread across two grains. The contribution of the two crystal lattices of the two grains will produced a mixed EBSD pattern. The degree of mixing in the pattern will change if the beam is slowly moved across the boundary On page 32, when you told about the 99% indexing at 5kV, what materials are you working on? What kind of sample preparation is required? Surface polishing to what extent? What is the best way of taking EDS data from powdered samples (nanoparticles)? We generally use our standard nickel superalloy sample for testing the performance characteristics of our system. EBSD has more stringent sample preparation requirements. Typically we work samples through a series of SiC grinding papers and polish with either diamond of alumina suspensions. The final polish generally uses a colloidal silica suspension (0.05 microns or 0.02 microns) which chemicallymechanically polishes the final surface, and will help produce nice EBSD patterns. EDAX has an automated particle analysis software package which identifies and collects data from many particles in a single field of view or multiple area collection. This allows large volumes of data, collected from single particles to be collected. However, if you are interested in individual collection this is also possible. A method for nanoparticle analysis should include considerations to reduce your analytical volume (lower kv), prevent beam damage (reduced raster versus point mode), lower dead time to maximize stored counts (faster processing time) and longer collection time.

3 Please discuss drift control with the combined techniques What is the accuracy of X-ray stdless quantification on highly tilted sample (70 )? If EDS is the basis for the EBSD determinations, what happens if EDS identifies Mo as S or one of the other difficult peak separations? What about erroneous peaks? What is the smallest size of an individual nanoparticle for EDS? EBSD is generally of higher concern in terms of correcting for drift during combined measurements. The most important thing with drift control is to mitigate it up front as much as possible. Make sure the sample is very well grounded. We typically avoid using the carbon or copper tapes as grounding methods as we need better conduction when trying to achieve high resolution than these tape provide. We may coat the surfaces - see question 24. For EBSD we have found that by first masking off the region of the sample to be characterize while coating the remainder of the surface with a relatively thick conductive coating and then following up with a light coating after removing the mask can help as well. Because of the high-tilt attaching a sample to a stub using sticky tape can also be a problem because the sample may creep during measurement. For difficult samples we've also found that allowing the beam and stage to settle for some time before performing a scan can help as well. This is almost always necessary when performing transmission EBSD measurements. In fact, some of reported waiting as much as two to three hours before proceeding. While some may argue that drift correction can be corrected through a predictive approach by measuring the drift for a few minutes and then applying a predictive model to correct for the drift, it is our experience that drift is rarely so simply modeled. Also, since EBSD measurements are made point by point, instead of through frame accumulation like in conventional EDS it is very difficult to provide very much improvement through drift correction. Thus, we have focused our efforts on eliminating the problem up front and our experience has been that we can almost always achieve this. The best gauge of accuracy is the ability to detect peak above background (or signal above noise). A higher tilt creates a shorter escape path for the x-ray created in the material, so the tilt will provide better peak above background. This happens for all elements in a matrix at different response levels, therefore proper matrix corrections at the tilt are required. The EDAX ezaf routine is also called "high tilt ZAF" and has updated these corrections. The elements identified with EDS are only the starting point for the EBSD solution. Often the EDS elements will search the candidate phase library and come up with more than one potential phase match. It is the EBSD indexing for all potential candidates that will make the best solution. Therefore, if the incorrect element is selected, there may not be any phases that match based on the other elements. In which case, no match allows the analyst to go back and refine the data but using user identified elements or user selected EBSD phases structures. That is dependent on the electron beam probe size, but typically a feature several nanometers to tens of nanometers in size will possible with TEM. 19 Does the EBSD work on different phases of carbon? 20 What is the spatial resolution of EBSD? Yes, we have successfully been able to get patterns from both diamond and graphite. We have been able to generate good maps from polycrystalline diamond materials. The spatial resolution will depend on a number of factors, including the average atomic number (density) of the sample, the sample preparation, the type of SEM used, and the deformation state of the material, but a good estimate with an FEG SEM would be nms. 21 What is a minimal grain size you can detect by this integrated system? EBSD will usually have better spatial resolution, and again is in the nm range. However if using EDS to differentiate phases in ChiScan, the effective resolution will be a bit higher, but can generally still resolve submicron features. 22 Will the presentation be available as pdf? The slide deck will not be available as a pdf - but if you would like more information, please contact us at info.edax@ametek.com or via our LinkedIn site at

4 23 What is the statistical limits of the combined technic...eds need higher dwell time than EBSD? This really depends on what you are trying to do with the data at each point. If you are trying to quantify the EDS data at each point, then EDS if often the rate limiting step. If you are just trying to use EDS data to differentiate phases, then EBSD can be the rate limiting step. Often it will depend on the count rate throughput of the specific EDS detector. 24 Is a conductive coating allowed in EBSD samples? Yes, but it should be kept relatively thin (approximately 20nm for a Carbon coating) and as uniform as possible 25 Both of the presenters did not talk about transmission EBSD recently developed. Have you developed special systems and applications as it has been done recently by Brucker? Thank you Nicolas You will note that the first reported transmission EBSD (or Transmission Kikuchi Diffraction) measurements made by Geiss and Keller were performed using an EDAX system. I would also recommend to you the recent paper in JOM on the subject: Suzuki, S. (2013). "Features of Transmission EBSD and its Application." JOM 65(9): These results were also obtained using an EDAX system. Some modifications do need to be made to the sample holder to allow for transmission but other than that no special systems or modifications are needed. You might find some adjustment to the Hough is needed to correctly locate the bands but the facility for such optimization is already available in the software. 26 Can you let me know the interaction volume of both EBSD and EDS compare with electron acceleration voltage? The interaction volume increases with increasing acceleration voltage. However, the actual volume is not only a function of voltage but also the diameter of the electron beam (i.e. the current) as well as the material itself. Also for conventional EDS performed with the sample surface perpendicular to the electron beam will have a different shape than EDS & EBSD measurements made at the high tilt required for EBSD (typically around 70 degrees). In general EDS information comes from an interaction volume nearly an order of magnitude larger than EBSD. However, the distribution of information in that volume is not uniform and thus the difference in the effective interaction volume is probably on the order of about 6 times larger. With EBSD measurement we have found the depth of the interaction volume seems to be more sensitive to voltage than the lateral resolution and thus tend to work at higher voltages. 27 Say I have 2% of B atoms in A structure. Both pure A and A-2at.%B, but there is small change in the unit cell. Can the combined EDS+EBSD deal with that? While in principle the addition of a small amount of B into the structure will distort the crystal lattice, it is unlikley that these distortions will be large enough for EBSD to detect. I would direct you to the work of Wilkinson's group at Oxford University in the arena of observing small changes in the EBSD patterns for measuring strains using EBSD. The crosscorrelation methods they have pioneered are the most promising for such work. See for example their recent article in Materials Today: Wilkinson, A. J. and T. B. Britton (2012). "Strains, planes, and EBSD in materials science." Materials Today 15(9): For EDS, the Z height or sample height plays an important role in determining the amount of counts. But with this tilting, are we limited to a certain range of Z height? The sample stage geometry is dependent upon the SEM travel tolerances and sample size. Often it is possible to have some Z control while at the high tilt conditions. The EDAX EDS detectors have a greater tolerance for signal sensitivity compared to EBSD, so it is most important that the sample be set for maximum EBSD signal collection. The EDS detector line of sight is built to allow for simultaneous EDS and EBSD collection, therefore signal lost due to increase in path length is minimized I could get good experimental data of EDX and EBSD together but the analysis that you showed in the presentation is not available in OIM 6. Are you using some other interface software? Can this technique be associated with an ion microscope? Much of the analysis we showed in our presentation is available in our TEAM software. This is a "new" (it has been out for a couple of years now) platform than is much more integrated than our older OIM/Genesis systems. The data collection side of EBSD and our EDS software is fully integrated together in the TEAM software. It has a lot of smart tools to help new users obtain reliable EDS & EBSD data with confidence but also still contains all the power and flexibility for power users. In principle, crystallographic orientation analysis can be performed using ions. However, I am not aware of any work being done in this area using modern ion based instruments whether on FIBs or the Helium ion microscope.

5 31 32 I missed a part of the talk, so it could be that I missed this information. Is the software that you have presented today a new version of TSL OIM or a new software package? When i procede contification is necessairy to quantifited k and l or only one raie pour quantifier est ce que je quantifier les deux raies de meme element or je contifier juste une raie sa suffit For quantification, do I need to quantify both lines, or will one line suffice? See question 20 For quantitative analysis it is necessary to choose one line or another, do not use both. For proper x-ray excitation, the electron beam energy should be 2-3 times the energy of the chosen line.

Carnegie Mellon MRSEC

Carnegie Mellon MRSEC Texture, Microstructure & Anisotropy, Fall 2009 A.D. Rollett, P. Kalu 1 ELECTRONS SEM-based TEM-based Koseel ECP EBSD SADP Kikuchi Different types of microtexture techniques for obtaining