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Phonons and fractons in sol-gel alumina: Raman study

Roy, Anushree and Sood, Ajay K (1995) Phonons and fractons in sol-gel alumina: Raman study. In: Pramana - Journal of Physics, 44 (3). pp. 201-209.

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We report Raman scattering from the boehmite, gamma-, delta- and alpha-phases of the alumina gel. Samples are characterized by transmission and scanning electron microscopy, X-ray diffraction and density measurements. The main Raman line in the boehmite phase is red-shifted as well as asymmetrically broadened with respect to that in the crystalline boehmite, signifying the nanocrystalline nature of the gel. Raman signatures are absent in the gamma- and delta-phases due to the disorder in cation vacancies. We also show that low frequency Raman scattering from the boehmite phase resembles that from a fractal network, characterized in terms of fraction dimension ($) over tilde d. Taking Hausdorff dimension D of the boehmite gel to be 2.5 (or 3.0), the value of ($) over tilde d is 1.33 +/- 0.02 (or 1.44 +/- 0.02), which is close to the theoretically predicted value of 4/3.

Item Type: Journal Article
Publication: Pramana - Journal of Physics
Publisher: Indian Academy of Sciences
Additional Information: Copyright of this article belongs to Indian Academy of Sciences.
Keywords: Al-gel;boehmite;disordered material;fractals;phonons;fractons.
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 24 May 2011 04:39
Last Modified: 24 May 2011 04:39
URI: http://eprints.iisc.ac.in/id/eprint/37860

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