Earth & Planetary Science Applications of X-Ray Diffraction: Advances Available for Research with our New Systems

Transcription

1 Earth & Planetary Science Applications of X-Ray Diffraction: Advances Available for Research with our New Systems James R. Connolly Dept. of Earth & Planetary Sciences University of New Mexico 401/501 Colloquium November 11, 2011

2 Outline What can you do with X-ray Diffraction? X-Ray Powder Diffraction Introduction to the method Advances in X-ray detectors Our Current Scintag system strengths and weakness Our New systems (arriving January) new capabilities Details of our New Systems (as time allows at end) Acknowledgements: Thanks to Aya Takase, Al Larsen, and Sean Bird from Rigaku, USA, for help with technical graphics, Maarten DeMoor for use of his sample data, the National Science Foundation for funding our new instruments, and CoPIs Adrian Brearley, Abhaya Datye and Darren Dunphy for making it all happen.

3 What can you do with X-ray Diffraction? Identify crystalline materials in powdered samples Determine of amounts of major and minor phases in multi-phase samples + Obtain precise crystal structure data for phases in powders + Analyze most materials totally non-destructively Identify crystalline materials in thin coatings on natural or engineered materials * Obtain good quality crystallographic data on extremely small amounts of material * Analyze materials in controlled environments (oxygen-free, controlled gas, controlled temperature) * Perform real-time experiments with materials under controlled conditions * Identify phases in a non-destructive manner in intact small samples * * Indicates capabilities to be added with our new systems + Indicates capability greatly enhanced with our new systems

4 What can t you do with X-ray Diffraction? Identify trace amounts of phases in a multi-phase sample though new instruments can detect smaller amounts of material, trace amounts are difficult to impossible to detect Quantitatively determine amounts of amorphous material in a sample this can be done by difference with an internal standard but does not leave original material unaltered Do single-crystal diffraction analysis (though this capability can be added to one of our new systems as an option) Do direct chemical analysis of samples XRD can do crystallographic analysis NOT chemical analysis

5 Diffraction patterns contains two components : Peak position provides information about crystal structure or d-spacings in a crystalline phase Peak intensity provides information about the scattering power of those d-spacings ; this is in turn related to the arrangements of constituent atoms in the structure and abundance of phases in a mixture Lots of other information may be obtained from peak shape and symmetry

6 The Bragg Equation n λ = 2d sinθ where n is an integer λ is the wavelength of the x-rays d is the interplanar spacing in the specimen θ is the diffraction angle The Bragg equation is the fundamental diffraction equation It is used to calculate interplanar spacings in crystal structures It is valid only for monochromatic X-rays.

7 An XRD Data Plot: 2θ (x-axis) vs. intensity (y-axis) Intensity Scale 2θ Angular Scale

8 Adding Peak Intensity Information to Positions Different diffraction peaks show differing intensities Scattering occurs at the atomic level Intensities are related to how all of the scattered X-rays from atoms in a particular diffracting dspacing add as a vector sum The combination of position and intensity is used to fingerprint particular crystalline structures (and often but not always unique phases)

9 Detector Source Monochromator Specimen

10

11

12 An XRD Data Plot: 2θ (x-axis) vs. intensity (y-axis)

13 Search/Match: Results Display

14 Search/Match: Printout of Results

15 X-ray Diffraction Patterns Gas Liquid / amorphous Powder / polycrystalline Single crystal

16 Extracting Information from a diffraction pattern Whole pattern Phase identification, quantitative analysis Peak position Lattice parameters Peak width Crystallite size & strain Diffraction Amorphous scattering %Crystallinity Background

17 Phase identification

18

19 Differing Intensity from strong preferred orientation Hump in background indicates presence of amorphous material

20 Our Existing Scintag Pad V System Sturdy, solid, reliable, good quality data Point detector collects data in 0.01 to 0.05 steps avg. data collection times 1-2 hours per sample; overnight for high resolution (quantitative-capable) data One sample at a time (no sample changer) Cannot change parts easily limited to Cu X-ray source, single sample stage, point detector, θ-2θ Bragg- Brentano scans Alignment is a several-day affair Analytical Software (DataScan4 & Jade+) good but not well integrated with instrument State-of-the-art system in 1985; upgraded but limited by its age

21 Laboratory Needs EPS XRD Lab is a service center used by multiple departments on campus including: E&PS, Various Engineering Departments and Institutes including CE, ChNE, CMEM, CHTM, Chemistry, Anthropology, Pharmacy, Biology, Water Resources Program New System requirements: Easily reconfigurable for different analytical needs Operable by non-experts in XRD Easy, automated alignment after exchange of components Add new research capabilities including: High throughput for standard powder analyses Microdiffraction (phase identification from very small areas) Non-ambient (atmosphere, controlled temperature & pressure) experiments High-speed data collection (for real-time experiments) Data collection from wet or damp materials Low-angle data from films and coatings Small angle scattering (SAXS) analysis for nano-materials

22 New Systems to Arrive January 2012 Funded by NSF MRI Grant to CMEM (ChNE) and E&PS To best meet diverse needs of investigators, we opted for two new instruments: Rigaku SmartLab Multi-purpose diffractometer capable of: Automated, multi-sample analysis w. sample spinning option 0D (Point) or 1D High Speed detector Non-ambient (elevated T, controlled environment) experiments Focused (parallel) X-ray beam or divergent beam geometry Horizontal sample orientation (low-volume and wet samples ok) Glancing Incidence, SAXS, GISAXS, HiRes XRD capabilities and more Rigaku Rapid II Small area-micro-diffraction w. large 2D detector Work with very small amounts of powder or intact samples Obtain diffraction data with highly oriented crystalline material Standard powder diffraction (when other systems busy)

23 Rigaku SmartLab

24

25 Rigaku D-Max Rapid II

26

27 3-Dimensional Diffraction Space Powder Sample

28 Advances in X-Ray Detectors Point or 0d detectors have a limited view of diffraction space one point at a time, usually 0.2 to 0.5 Data collection is by fixed time at each point, usually ½ to several seconds, thus slow If lines are spotty because of preferred orientation, diffractions will be missed Most common 0d detector is the Scintillation counter -- still widely used for many applications Most efficient if used with a sample changer in unattended mode

29 Advances in X-Ray Detectors Linear or 1d Detectors sample a larger angular slice of diffraction space, usually 1-3 (but to 120 with specialized detectors) Moves through a range of diffraction space as a sliding window collecting data throughout its angular range Results in greatly increased speed of data collection (typically 50x to 100x that of a scintillation counter) Most modern 1d detectors are some form of Silicon strip technology and are very durable and robust devices

30 Rigaku D/teX Ultra 1d Detector Linear range of diffraction space (up to 1.5 ) measured simultaneously = x faster data collection

31 D/teX Ultra Zeolite sample measured in 60 seconds

32 Variable temperature XRD experiment with D/teX Ultra Detector

33 Advances in X-Ray Detectors Area or 2d detectors view a substantial slice of diffraction space in two dimensions Smaller 2d detectors can be moved through diffraction space and images combined to produce large map of 2d space Larger 2d detectors can remain fixed recording a snapshot of 2d space 2d detectors enable collection of diffraction data from samples with extreme preferred orientation in some cases collecting useful data from single crystals

34

35 Rigaku Rapid II Microdiffraction Advantages Extremely large detector (25.6 x 46.6 cm) Image plate records all X-ray energies different sources (Cu, Co, and Mo) may be used. Sources are easily changed 3-axis sample stage allows many different sample types to be mounted and analyzed Beam collimators cover range from 800 µm to 30 µm Image recording times can be from 5 to 60 minutes (or more if needed) Image is digitally read, data recorded and plate ready for reuse within a couple of minutes

36

37 Meteorite ALH Microdiffraction Data from Rigaku Rapid II Black area

38 Meteorite ALH Microdiffraction Data from Rigaku Rapid II Brown area

39 Meteorite ALH Microdiffraction Data from Rigaku Rapid II White area

40

41

42

43

44

45 Using the XRD Lab XRD lab is open to any faculty, students or staff wanting to incorporate XRD in their research Radiation safety training and exam must be completed by all users Training for equipment operation will be available The lab is a service center so fees are charged for use Fee schedules for analyses will be similar to that for the current instrument with additional schedules for use of new experimental equipment Anyone wanting to incorporate XRD into research proposals should connect with me about how best to do that