I ntroduction to X-ray Diffraction

1. Introduction toX-ray Diffraction 27.10.2014 |1

2. Outline : • 1. XRD basics • 1.1 X-ray Generation and Properties of X-rays • 1.2 Bragg’s law • 2. information about XRD instruments • 3. the operation of XRD • 4. about the results of XRD 27.10.2014 || 2

3. Introduction: electromagnetic spectrum 27.10.2014 || 3

4. 1. Stanford Synchrotron Radiation Laboratory (SSRL) • http://www-ssrl.slac.stanford.edu/ • 2. Argonne National Laboratory Advanced Photon Source (APS) • http://www.aps.anl.gov/ • 3. Lawrence Berkeley National Laboratory Advanced Light Source (ALS) • http://www-als.lbl.gov/ • 4. Brookhaven National Laboratory National Synchrotron Light Source (NSLS) • http://www.nsls.bnl.gov/ 27.10.2014 || 4

5. Bragg's Law 2dsinθ = n λ 27.10.2014 || 5

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7. A powder XRD scan of corundum (Al2O3) standard reference material provided with the D8 instrument is shown below as a plot of scattering intensity vs. the scattering angle 2θ or the corresponding d-spacing. The peak positions, intensities, widths and shapes all provide important information about the structure of the material. 27.10.2014 || 7

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9. Photo of the Bruker D8 ADVANCE XRD 27.10.2014 || 9

10. Photo of the components in the main compartment of the Bruker D8 ADVANCE. 27.10.2014 || 10

11. Turning on the D8 Instrument • 1. Haskris water chiller. • 2. Turn on the PC computer monitor and the computer. • 3. Power on the D8. • 4. Open D8 TOOLS Software (on PC desktop) • 5. To turn on X-ray generator. 27.10.2014 || 11

12. D8 Tools Instrument status page (Online Refresh ON/OFF button is circled) On line Refresh ON/OFF 27.10.2014 || 12

13. Running the D8 Instrument • 1. Select “DIFFRACPLUS Measurement” icon on the desktop. • 2. Open up “XRD Commander” (opens data collection software—see Figure ) 27.10.2014 || 13

14. Primary optic X-ray power Detector Scan type Stop angle Start angle Start XRD Commander Page in DIFFRACPLUS Measurement software 27.10.2014 || 14

15. Normal Instrument Shutdown 1. In the Immediate Measurement program, set the generator power to 20 kV and 5 mA. Hit the Start button. When data collection has started, hit the Stop button. Exit the Immediate Measurment program. Shut Down the PC computer. 2. Shut down the D8 controller by depressing the "0" button on the right side of the rounded column of the instrument. Note that doing this will also shut down the X-ray generator. X Rays are no longer being generated, but the storage capacitors in the generator will continue to hold an electrical charge for at least 15 minutes. 3. On the generator control panel, depress and hold the heater button for at least 5 seconds or until the green lamp on the button is lit. 4. After 5 more minutes, turn the generator switch key to the "0" position, turning off the generator. 5. Close water valves between the water chiller and the instrument. If there are no other instruments using the water chiller then turn off the electrical power to the water chiller and close the water valves between the chiller and the city water supply. 27.10.2014 || 15

16. Examining X-ray Diffraction The results of a x-ray diffraction experiment using x-rays with l = 0.7107 Å (a radiation obtained from molybdenum target) show that diffracted peaks occur at the 2q angles as shown in the table. Determine the crystal structure, the indices of the plane producing each peak, and the lattice parameter of the material. 27.10.2014 || 16

17. SOLUTION We can first determine thesin2qvalue for each peak, then divide through by the lowest denominator, 0.0308. is impossible ! 27.10.2014 || 17

18. SOLUTION (Continued) We could then use 2q values for any of the peaks to calculate the interplanar spacing and thus the lattice parameter. Picking peak 8: Why? 2q = 59.42° or q = 29.71° This is the lattice parameter for body-centered cubic iron. 27.10.2014 || 18

19. Thanks for your attention 27.10.2014 || 19