Presentation on theme: "HighScore Plus for Crystallite Size Analysis"— Presentation transcript:
1HighScore Plus for Crystallite Size Analysis Scott A Speakman, Ph.D.Center for Materials Science and Engineering at MIT
2Before you begin reading these slides or performing this analysis … These slides assume that you are familiar withProfile FittingFundamental Theory of Crystallite Size and Microstrain Analysis using X-Ray Powder DiffractionPlease make sure that you have read the tutorials:“Profile Fitting using PANalytical HighScore Plus”“Fundamentals of Line Profile Analysis for Nanocrystallite Size and Microstrain Estimation using XRPD”These tutorials are available atSlide ‹#› of 20Scott A Speakman, Ph.D.
3These instructions will also teach you how to create template file These instructions will assume that you are working with an external calibration standardThese instructions will also teach you how to create template fileSlide ‹#› of 20Scott A Speakman, Ph.D.
4Before determining crystallite size the instrument broadening must be corrected for Data must be collected from a standard using the same instrument and same configuration as will be used to collect data from the specimenThe data should be opened in HighScore Plus and the peaks profile fitSlide ‹#› of 20Scott A Speakman, Ph.D.
5Creating the Instrument Profile Calibration Curve Right-click in the Additional Graphics paneFrom the menu, select Show Graphics > Halfwidth Plot > FWHM StatisticsSlide ‹#› of 20Scott A Speakman, Ph.D.
6The FWHM Statistics plot will show the FWHM of the profile fit peaks and the best fit Caglioti curve Examine the curve fit to the FWHM data pointsMake sure that the Caglioti curve fits the FWHM plotClosely examine any outliersThe equation that is displayed is the Caglioti equation with parameters W, V, and USlide ‹#› of 20Scott A Speakman, Ph.D.
7Creating the Instrument Profile Calibration Curve Right-click in the Additional Graphics paneFrom the menu, select Show Graphics > Halfwidth Plot > Broadening (Gaus+Lorentz)In this plot, the Gaussian and Lorentzian components of the peak profiles are plotted in individual Caglioti curvesThis is the calibration curve required for proper line profile analysisThese Caglioti equations must be converted into an instrument profileFrom the menu, select Show Graphics > Take as LP Analysis StandardSlide ‹#› of 20Scott A Speakman, Ph.D.
8The Caglioti coefficients for the calibration curve can be seen in the Global Settings Select the Refinement Control tab in the Lists PaneLeft-click on the phrase Global Variables in the Refinement Control paneLook in the Object Inspector pane for the Global Settings.The LP Standard coefficients are recorded in the “Instrument Standard” field as Gauss Coefficients and Lorentz CoefficientsSlide ‹#› of 20Scott A Speakman, Ph.D.
9A template can be used as a starting point for multiple analyses of experimental data You could record the Gauss and Lorentz coefficients from the Instrument Standard field and them enter into every new documentIf you are not sharing a computer and only use one instrument with one configuration, you could also save them as defaults in the menu Customize > DefaultsIn order to save work, you can also create a template fileA template file is an empty HPF document that contains several settingsWe will create a document that contains the LP Standard coefficients determined by the analysis of the standardA template can also containReference patternsPeaks in the peak listPhases for refinementSlide ‹#› of 20Scott A Speakman, Ph.D.
10Creating a templateAfter you create the instrument LP Analysis StandardGo to the Peak List tab in the Lists PaneRight-click in the Peak List and select the menu option Delete > Included PeaksGo to the Refinement Control tab in the Lists PaneExpand the entries Global Variables and BackgroundIn every parameter within Background (Flat Background, Coefficient 1, etc), set the value to 0Go to the Pattern List in the Lists PaneDelete all reference patterns loaded in the Pattern ListIf you are always analyzing the same phase(s), you could load the reference patterns for those phases and save them in the templateGo to the Scan List in the Lists PaneDelete all experimental scans loaded in the Scan ListSave the document in a *.HPF format with a clever name like “LP Analysis Template.hpfSlide ‹#› of 20Scott A Speakman, Ph.D.
11Begin analysis of the nanocrystalline material Open the template file if it is not already openInsert the data for the nanocrystalline sample by selecting the menu File > InsertBe sure that you do not save over your empty template. Before you go any further, you can save this file using the menu item File > Save As …Profile Fit the data from them nanocrystalline sampleSlide ‹#› of 20Scott A Speakman, Ph.D.
12Examine the FWHM Plot for Outliers Right-click in the Additional Graphics paneFrom the menu, select Show Graphics > Halfwidth Plot > FWHM StatisticsExamine the FWHM plot for outliers or anomoliesIn the plot below, one peak does not conform to the general FWHM curveIf your sample contains a mixture of phases, you may observe a different FWHM line for each different phaseSlide ‹#› of 20Scott A Speakman, Ph.D.
13Select what peaks you will use in the line profile analysis There are two ways to deal with a mixture of phasesYou could use the ability to mark peaks as included/excludedYou could associate all peaks with a specific phase and then analyze the peaks from one phase at a timeThese slides will first demonstrate how to include/exclude peaksSlide ‹#› of 20Scott A Speakman, Ph.D.
14Examine the data, peak list, and FWHM plot and exclude peaks that should not be used for LP analysis In the data shown to the right, there is a small impurity phaseThe peak from this phase is not indexed by the reference card lines (solid purple lines)The peak from this phase is an outlier on the FWHM plotWe want to exclude the peak(s) from the impurity phaseSlide ‹#› of 20Scott A Speakman, Ph.D.
15There are a few ways to exclude a peak Right-click on the data point for the peak in the FWHM plotFrom the context sensitive menu, select Set Peak(s) > ExcludedIn the Peak List in the lists pane, right-click on the line for the peakGo to the menu Tools > Set Peak StatusBuild the filter to a setting such as “Set Peaks with: Matched=False to Excluded”.All peaks that are not matched by a reference pattern will be excludedYou could also exclude all matched peaks insteadSlide ‹#› of 20Scott A Speakman, Ph.D.
16Excluded peaks are highlighted in light blue in the Peak List, the FWHM plot, and the line markers The advantage to excluding peaks, rather than deleting them, is that they can be included again if you need to use them for additional analyses (such as repeating the profile fitting)Slide ‹#› of 20Scott A Speakman, Ph.D.
17You can now use the Peak List to evaluate the crystallite size and microstrain of the sample There are four columns with crystallite size and microstrain information available in the Peak ListAdditional information is shown in the Object Inspector for each individual peak in the Line Profile Analysis areaThis information can be viewed by left-clicking on a peak in the Peak List and then looking at the Object InspectorSlide ‹#› of 20Scott A Speakman, Ph.D.
18Different calculations reported in the peak list use different values of the peak breadth In the Object Inspector, you can see peak information for the peak breadth “B”HighScore Plus uses breadth instead of FWHM for LP analysisCalculations use the Structural BreadthObs B is the breadth of the experimental diffraction peak for the sample being analyzedInst B is the breadth calculated from the LP Analysis Standard created when the calibration data was used to analyze the instrument profileStruct B is the peak broadening due to the sampleStruct B= Obs B – Inst BThe Breadth is reported as three componentsB is the overall breadth of the entire peakLorentz B is the breadth of the Lorentzian component of the peakGauss B is the breadth of the Gaussian component of the peakSlide ‹#› of 20Scott A Speakman, Ph.D.
19The difference between “Crystallite Size” vs “Crystallite Size Only’ (and “Microstrain” vs “Microstrain Only”)The values Crystallite Size Only and Microstrain Only are determined using the Struct B, ie the overall breadth of the entire diffraction peakCrystallite Size Only is calculated assuming there is no Microstrain broadeningThis is the classis application of the Scherrer equationMicrostrain Only is calculated assuming there is no crystallite size broadeningThe values “Crystallite Size” and “Microstrain” are calculated using a less conventional shape deconvolutionThe assumption is that all Crystallite Size broadening has as Lorentzian shape and that all Microstrain broadening has a Gaussian shapeTherefore, it is assumed that“Struct Lorentz B” quantifies the peak broadening due to crystallite size and can be used in the Scherrer equation to determine the crystallite size“Struct Gauss B” quantifies the peak broadening due to microstrainThis analysis might be valid if there is low dislocation density in the sampleDislocations area type of Microstrain broadening that have a Lorentzian shape profileSlide ‹#› of 20Scott A Speakman, Ph.D.
20The values for Crystallite Size and Microstrain in the Peak List are calculated based on individual peaksTo determine if the assumption of Crystallite Size Only (ie no microstrain) or Microstrain Only (ie no crystallite size broadening) are true, evaluate how they change with the 2Theta position of the peakIn the example above, the value Crystallite Size Only does not change systematically with 2Theta.The value Microstrain Only does change systematically with 2TehtaThis means that the assumption that there is no Microstrain is more likely to be correctSlide ‹#› of 20Scott A Speakman, Ph.D.
21A more accurate evaluation can be determined by using all peaks for the calculation in a Williamson-Hall plotThe Williamson-Hall plot is shown below the Peak ListIt shows how well the data fit equationSlide ‹#› of 20Scott A Speakman, Ph.D.
22Settings in Customize > Document Settings In this dialogue, you can explore different ways to apply Line Profile Analysis to your data.Slide ‹#› of 20Scott A Speakman, Ph.D.
23Analyze the Williamson-Hall Plot with Different Assumptions You can test your data assuming there is only microstrain broadening or only crystallite size broadeningSlide ‹#› of 20Scott A Speakman, Ph.D.
24If assuming that there is no crystallite size broadening does not decrease the residual of the linear fit compared to fitting both size and strain, then the amount of crystallite size broadening is insignificantWilliamson-Hall PlotSin(Theta)0.80.750.70.650.60.550.50.450.40.3188.8.131.52.150.10.05Struct. B * Cos(Theta)184.108.40.206.220.127.116.11.18.104.22.168Chi square: 0.058Size [Å]: 278(114)Strain [%]: 1.00(2)Williamson-Hall PlotSin(Theta)0.80.750.70.650.60.550.50.450.40.322.214.171.124.150.10.05Struct. B * Cos(Theta)126.96.36.199.41.21Chi square: 0.062Strain [%]: 1.18(5)Strain OnlySize and StrainThis does not necessarily mean that there is no crystallite size broadening, just that it cannot be quantified because it is overwhelmed by the amount of microstrain broadeningSlide ‹#› of 20Scott A Speakman, Ph.D.