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Nanoparticles of the giant dielectric material, CaCu3Ti4O12 from a precursor route

Thomas, P and Dwarakanath, K and Varma, KBR and Kutty, TRN (2008) Nanoparticles of the giant dielectric material, CaCu3Ti4O12 from a precursor route. In: Journal of Physics and Chemistry of Solids, 69 (10). pp. 2594-2604.

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A method of preparing the nanoparticles of $CaCu_3Ti_4O_{12}$ (CCTO) with the crystallite size varying from 30 to 200 nm is optimized at a temperature as low as 680 1C from the exothermic thermal decomposition of an oxalate precursor, $CaCu_3(TiO)_4(C_2O_4)_8 \cdot 9H_2O$. The phase singularity of the complex oxalate precursor is confirmed by the wet chemical analyses, X-ray diffraction, FT-IR and TGA/DTA analyses. The UV–vis reflectance and ESR spectra of CCTO powders indicate that the Cu(II) coordination changes from distorted octahedra to nearly flattened tetrahedra (squashed) to square-planar geometry with increasing annealing temperature. The HRTEM images have revealed that the evolution of the microstructure in nanoscale is related to the change in Cu(II) coordination around the surface regions for the chemically prepared powder specimens. The nearly flattened tetrahedral geometry prevails for $CuO_4$ in the near surface regions of the particles, whereas square-planar $CuO_4$ groups are dominant in the interior regions of the nanoparticles. The powders derived from the oxalate precursor have excellent sinterability, resulting in high-density ceramics which exhibited giant dielectric constants upto 40,000 (1 kHz) at 25 1C, accompanied by low dielectric loss <0.07.

Item Type: Journal Article
Publication: Journal of Physics and Chemistry of Solids
Publisher: Elsevier Science
Additional Information: Copyright of this article belongs to Elsevier Science.
Keywords: Oxides;Chemical synthesis;Electron microscopy;Dielectric properties.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 18 May 2009 07:08
Last Modified: 19 Sep 2010 04:53
URI: http://eprints.iisc.ac.in/id/eprint/16760

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