Diffraction practical: Single crystal diffraction

Experiment

1. Take a diffractogram of quartz powder.
2. Take a diffractogram of the 100 (or equivalent) plane of a quartz single crystal. You can identify which plane that is by comparing the specimen with the animation on the Webmineral site.
3. Lock onto the biggest Bragg peak.
4. While keeping 2theta fixed, scan the phi-axis, i.e. scan while rotating the turntable. You need to switch from "locked-coupled scan" to "phi scan" for this.
5. What is the effect of (very slightly) tilting the crystal?
6. See if you can pick out another crystal plane by orientating the crystal appropriately.
7. Do a phi scan for the powder sample. Can you pick out individual crystallites?

Report

1. Sketch the crystal plane(s) measured in the single crystal experiment.
2. Explain why powder diffraction measures all Bragg peaks simultaneously and discuss possible artifacts in powder diffractograms.

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