Powder X-Ray Diffraction (powder XRD)
Powder X-ray diffraction is one of the primary tools used for the identification of crystalline materials. Peak positions in diffraction patterns are determined by interplanar spacings between rows of atoms in crystals and can be used for phase identification or lattice parameter determination. Peak intensities are related to the phase proportion and sample chemistry, among other factors, and can be used to determine the proportions of various phases in a mixture. Peak profiles contain information about crystallite size and strain.
Detailed information about clay minerals requires separate procedures that involve physical separation of the clay size fraction, preparation of oriented mounts, and multiple scans following treatments such as ethylene glycol vapor, heating at various temperatures, and various cation saturations.
|Dr. Andy Elwood Madden||Professor||lab director||first-time users; financial/ procedural questions|
|Joshua Wester||Undergraduate researcher||lab assistant||repeat users; scheduling sample drop-off and pick-up; scheduling time for analyses|
How to get started
Prepare the answers to the following questions:
- What are the goals of the analysis?
- Are the samples already powders of micron-sized particulates, or is sample preparation required?
- Who will do the sample preparation?
- Who will do the specimen mounting?
- If you are wanting something different than our typical 2-70 degree scan, Bragg-Brentano geometry, graphite monochromator, and scintillation detector, then can you provide an example from the literature that illustrates the data you hope to collect?
- If you require pattern interpretation, who will be responsible for learning the procedures?
Contact Dr. Elwood Madden (amadden at ou.edu). It would be helpful if you can provide the answers to these questions immediately. Read the information on the rest of this website.
Learn about powder X-ray diffraction
- Check out Jim Connelly’s excellent webpages: http://epswww.unm.edu/labs/x-ray-diffraction-lab/xrd-resources/
- more background – Jenkins R and Snyder RL (1996) Introduction to X-ray Powder Diffractometry, John Wiley, 403 p.
About data analysis
Note that we do have software and database capabilities to perform data analysis tasks beyond the standard data reporting. Student are welcome to use the software, as long as they follow the lab guidelines (below). Data analysis and interpretation is not routine. As such, the end user is responsible for their own interpretations. Those end users desiring assistance with data analysis and interpretation can enlist the help of XRD lab personnel as a research collaboration. Extensive support materials for data analysis, including videos for using the software that individuals can work on at their own pace, are available in our online lab manual. Users may request access.
Expectations for lab users
- All laboratory personnel must have satisfactorily complete Radiation Safety Training through the University of Oklahoma Radiation Safety Office prior to beginning work with the X-ray diffractometer.
- Do not use any equipment beyond spatulas, slides, and basic tools until you have received appropriate training. Equipment must be used and cleaned in the manner described in the lab manual.
- Anyone working with chemicals must keep current their training at: https://www.ouhsc.edu/ehso/training-norman/new_logon.asp . The required modules are “Hazard Communication/ General Safety Training” and “Laboratory Safety”. If you need to use chemicals in SECA101 you must receive permission first.
- You must disclose any hazards of potentially toxic or dangerous substances in your samples that others working in the lab may encounter. This includes disclosure of materials that cannot be disposed in the sink or trash.
- Modification, repair, realignment, or otherwise tampering with any mechanical or computerized system in the XRD lab is expressly prohibited, except by the Lab Director/Manager.
- The PC attached to the XRD should be considered as a part of the diffractometer. Nothing should be done on it other than controlling the XRD, which is done by XRD lab staff. Also, the PC attached to the Raman is only for Raman analysis.
- Never install or update software on the xrd computers.
- Clean up after yourself and observe the basics of laboratory safety. All sample preparation activities require the use of safety glasses. All sample preparation activities using chemicals require safety glasses and protective gloves.
- All containers with chemicals must be labeled with the contents using indelible ink (sharpie / permanent marker) or indelible ink on labeling tape. Never leave open containers on the workbench unless you are using them. All containers must be sealed prior to the technician leaving the laboratory.
- If you use the last of something or notice the stock of an item is low, it is your responsibility to inform the lab director. In addition, if you identify malfunctioning, misused, or damaged equipment, it is your responsibility to inform the lab director.
- The powder XRD lab is a place of business, not a “hang out”. Conduct personal business elsewhere.
- Only lab staff are authorized to train new users and allow access to untrained individuals.
- For appointments, show up in a timely manner or communicate that you are late/ unavailable.
- We maintain a standardized data archiving strategy. All patterns collected must be logged by hand into the physical logbook. Pattern datafiles should be labeled with the following format, where the parenthesis are for illustration only and should be excluded from the file name: (yy-mm-dd) (initials of xrd operator for analysis) (sample description) (optical configuration, either PB for parallel beam or BB for Bragg-Brentano).raw Data files are archived in the C:\Windmax\Data folder in the appropriate subfolder. OU users should store your data in the \OU Research Samples\folder, then within the folder for the current year and month. You may copy the data to another location, but always leave one copy archived in this location.
- Do not alter, delete, or copy data other than that collected on our own samples.
Template for publication methods.
Here is an example of what you might use in a publication:
Powder X-ray diffraction (XRD) analyses were performed in the School of Geology and Geophysics at the University of Oklahoma using a Rigaku Ultima IV diffractometer. Cu-K-alpha radiation (40 kV, 44 mA) was used with a (insert detector type) detector. Data analysis was completed using (insert software type) with the ICDD (International Centre for Diffraction Data) PDF4+ database.
Academic users will be billed $25/scan.
What are the reasons to justify these costs?
- Materials and supplies. Weigh boats, methanol, safety equipment (gloves, eye protection), replacement glassware, computers and paper, etc. that are utilized by most lab users must be replaced.
- Analysis software renewal. Our Jade 2010 software used to analyze data is on a subscription and must be renewed.
- Database renewal. In spring 2014, we purchased a ICDD PDF4+ Scholar package, providing the latest database access, support, and updates through spring of 2024. The cost was $10,960 for the 10-year commitment. Thus, we should plan for a similar commitment in ten years.
- X-ray tube. The Cu X-ray source naturally degrades over time. Expected lifetimes of X-ray tubes are around 5 years, and the expected cost is approximately $4000.
These costs also do not include the cost of eventual instrument replacement; it is assumed funds for this will have to come from elsewhere – otherwise the costs would be much higher!
No matter how sophisticated the equipment, the quality of powder XRD data remains limited by the quality of sample preparation. Our lab has several types of equipment for crushing, grinding, and disaggregating, including the recommended McCrone micronizing mill. Additionally, we have all the equipment necessary for clay separation, including a heated water bath for chemical treatments, sonic dismembrator for disaggregation and physical separation, centrifuge, and vacuum filtration. Optical microscopy can be used for examining samples to help determine between non-unique solutions to fitting the diffraction pattern.
All samples are not equal, and every measurement does not have the same analysis goals. We have the capability for adapting to meet several types of samples and analytical goals. We have three Si(511)-based zero-background holders for small amounts of sample or attempts to maximize intensity accuracy. Typically, we operate our Rigaku Ultima IV diffractometer with Bragg-Brentano geometry and a Cu X-ray source to maximize intensity, and with a graphite monochromator and scintillation detector to maximize resolution. For rough/ irregular samples or glancing incidence analyses of thin films we can analyze using parallel beam geometry. Additionally, for samples requiring rapid analysis times (for example, samples that are oxygen- or humidity- sensitive) we can utilize our D/tex Si strip detector.
Data analysis and databases
Our lab has several options for data analysis. MDI Jade2010 linked with the latest ICDD-PDF-4+ database provides the most flexible and powerful data analysis and presentation solution including phase analysis, search/matching, and quantitation through whole-pattern fitting. Rigaku PDXL is convenient for functions such as peak decomposition. ClaySim is useful for simulating 1-D oriented phyllosilicates, including mixed-layer phases and phases with variable chemistry, and quantitative analysis of bulk samples with the RockJock method. ICDD Sleve software allows flexible searching of the PDF-4+ database, with many options for data/structure retrieval and comparative analysis.
Summary of capabilities
Sample preparation options
McCrone micronizing mill
water bath for chemical digestions
Stereoscope/ digital camera
high-temperature resistant fused-silica slides
D/teX silicon strip detector or
scintillation detector with curved graphite monochromator
Bragg-Brentano or parallel beam, theta-theta or grazing incidence
fixed or variable divergence slit
choice of high-limiting slit (also beam irradiation width for variable div. slit)
choice of soller slit/ recieving slits
Materials Data (MDI) Jade 2010 (updated annually)
Materials Data (MDI) Jade 9.3
Materials Data ClaySim