Abstract
The Raman spectra of many kaolins are dominated by bands from ancillary anatase. Fired samples of a commercial anatase-bearing kaolin from the Jari River deposit in Brazil showed significant variations of Raman spectra as a function of the firing temperature. The spectra showed the full range of anatase bands up to a firing temperature of 900°C. From 950°C the background increased significantly, leading to an unfavorable signal/noise ratio that allowed observation of only the most intense (Eg) band at ~144 cm−1. X-ray diffraction (XRD), however, confirmed that this band, which persists up to 1200°C, results from anatase. Two factors may be responsible for the high thermal stability of anatase in this sample: its relatively large particle size of ~120 nm and possible reactions with Si and Al that become liberated during kaolinite breakdown. When evaluated with circumspection, Raman and XRD data on anatase can serve as ‘thermometers’ to elucidate the thermal history of fired anatase-bearing kaolins and other anatase-bearing clays.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Dachille, F., Simons, P.Y. and Roy, R. (1968) Pressuretemperature studies of anatase, brookite, rutile and TiO2-II. American Mineralogist, 53, 1929–1939.
Gribb, A.A. and Banfield, J.F. (1997) Particle size effects on transformation kinetics and phase stability in nanocrystalline TiO2. American Mineralogist, 82, 717–728.
Heald, E.F. and Weiss, C.W. (1972) Kinetics and mechanism of the anatase/rutile transformation, as catalyzed by ferric oxide and reducing conditions. American Mineralogist, 57, 10–23.
Lindsley, D.H. (1991) Experimental studies of oxide minerals. Pp. 69–106 in: Oxide Minerals: Petrologic and Magnetic Significance (D.H. Lindsley, editor). Reviews in Mineralogy, 25. Mineralogical Society of America, Washington, D.C.
Lottici, P.P., Bersani, D., Braghini, M. and Montenero, A. (1993) Raman scattering characterization of gel-derived titania glass. Journal of Materials Science, 28, 177–183.
Murad, E. (1997) Identification of minor amounts of anatase in kaolins by Raman spectroscopy. American Mineralogist, 82, 203–206.
Murad, E. and Köster, H.M. (1999) Determination of the Ti speciation in commercial kaolins by Raman spectroscopy. Clay Minerals, 34, 479–485.
Murad, E. and Wagner, U. (1991) Mössbauer spectra of kaolinite, halloysite and the firing products of kaolinite: new results and a reappraisal of published work. Neues Jahrbuch für Mineralogie Abhandlungen, 162, 281–309.
Murray, H.H. and Partridge, P. (1982) Genesis of Rio Jari kaolin. Proceedings of the International Clay Conference Bologna-Pavia. Developments in Sedimentology, 35, 279–291 (H. van Olphen and F. Veniale, editors). Elsevier, Amsterdam.
Stanjek, H. and Friedrich, R. (1986) The determination of layer charge by curve-fitting of Lorentz- and polarization-corrected X-ray diagrams. Clay Minerals, 21, 183–190.
Yang, J. and Ferreira, J.M.F. (1998) Inhibitory effect of the Al2O3−SiO2 mixed additives on the anatase-rutile phase transformation. Materials Letters, 36, 320–324.
Zhang, H. and Banfield, J.F. (1999) New kinetic model for the nanocrystalline anatase-to-rutile transformation rate revealing dependence on number of particles American Mineralogist, 84, 528–535
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Murad, E. Raman and X-ray Diffraction Data on Anatase in Fired Kaolins. Clays Clay Miner. 51, 689–692 (2003). https://doi.org/10.1346/CMN.203.0510611
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1346/CMN.203.0510611