I get some Raman spectrums of nano ZrO2 powders, but their peak value and peak width are different. Can I analyse their crystallinity like XRD? If so, how to do? Thanks very much!
Dear J.,
If you are interested in crystallinity only, XRD analysis should be enough. If you are trying to get a particular ZrO2 phase and having issues to identify it with XRD, I'd suggest to conduct a XRD rietveld refinement. This is very useful specially if you are varying synthesis conditions and investigating a change in crystal phase. Raman spectroscopy can be a complement to XRD in crystal phases transitions analysis.
I cite:
" Since it was not possible to clearly distinguish between cubic and tetragonal ZrO2 based on the XRD data only, the formation of bulk quantities of the cubic phase was confirmed by Raman spectroscopy. [...] Raman spectroscopy is sensitive to the polarizability of the oxygen ions and therefore it can be used to determine the symmetry of a crystal system. The Raman spectrum for cubic ZrO2 is characterized by a broad band near 530–670 cm−1 and additional poorly defined features related to the disordered oxygen sublattice whereas tetragonal ZrO2 exhibits several well-defined sharp bands because of the symmetry reduction. "
Best wishes,
Maria
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M. L. Gonzalez-Juarez , thanks very much for your answer and the article ! I find the Raman spectrum seems to be more sensitive than XRD when the crystallinity of ZrO2 is changed, especially in the case of the surface composition variation.
Dear J. Zhang,
the question is, which information you can get from Raman spectra. The peaks in your graph probably allow to get information concerning the phonon spectrum. This spectrum vanishes in nano material because phonons are attributed to a certain extended periodic structure.
Nevertheless, you can observe additionally "local modes". These modes are not due to a crystalline structure but are due to vibration states of single atoms (impurities,...).
Furthermore you have to take into account that you observe only optical active modes. To couple with light beams, a dipol moment must be present. Besides this you have to fulfil selection rules. You only observe phonons near k = 0 (k-wavevektor).
With Regards
R. Mitdank
J.X. Zhang Try a rietveld refinement if you can, you can get information about whether you have a single crystal phase or a mixture of them (% ratio of the crystal phases present).
Best wishes,
Maria
Article Qualitative X-Ray Diffraction Analysis of Metastable Tetrago...
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