Phonons and fractons in sol-gel alumina: Raman study

Roy, Anushree ; Sood, Ajay K. (1995) Phonons and fractons in sol-gel alumina: Raman study Pramana - Journal of Physics, 44 (3). pp. 201-209. ISSN 0304-4289

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We report Raman scattering from the boehmite, γ-, δ- and α-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 γ- and δ-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 d~. Taking Hausdorff dimension D of the boehmite gel to be 2.5 (or 3.0), the value of d~ is 1.33±0.02 (or 1.44±0.02), which is close to the theoretically predicted value of 4/3.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Al-gel; Boehmite; Disordered Material; Fractals; Phonons; Fractons
ID Code:79867
Deposited On:30 Jan 2012 04:59
Last Modified:18 May 2016 22:04

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