This quick lab experiment is designed to introduce students to powder X-ray diffraction including sample preparation, data collection, and the analysis of diffraction data to refine lattice parameters. Diffraction data is collected for a sample of the cubic perovskite SrTiO3 (useful data can be obtained in relatively short times) and compared to data collected previously (over 6 hours) for the orthorhombic perovskite CaTiO3. Students index the diffraction pattern of SrTiO3 by comparison to the JCPDS database, and use a free program, UnitCell, to refine the lattice parameter.
A student should acquire hands-on experience:
- Preparing samples for X-ray powder diffraction
- Using the X-ray powder diffractometer to set-up and acquire diffraction data
- Analyzing the raw diffraction data by applying the background subtraction and K-alpha 2 stripping algorithms, and running the peak-picking software
- Indexing their diffraction pattern by comparison to a known pattern and refining the lattice parameters of their sample
X-ray powder diffractometer
Sample of SrTiO3 (can be purchased or made by firing SrCO3 and TiO2 at temperatures > 1000˚C)
This lab experiment typically follows the Optical Transform experiment simulating X-ray diffraction and introduces students to the powder diffractometer, data collection and analysis, and the UnitCell program, which may be used in a subsequent experiment. The UnitCell program can be somewhat buggy, particularly the PC version. But it is a very helpful (and free!) program.
1 hour lab time, 1 hour for analysis
Typically, students complete the analysis in their lab notebooks and their answers to the discussion questions in the lab handout are assessed.
This lab is mostly about learning how to run the diffractometer and analyze data. Most students acquire these skills with minimal difficulty. If they do not, then we learn that pretty quickly in follow-up weeks when they are expected to collect powder diffraction data on their own as "experienced users."
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