ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 56, (3) 222 - 228 (2012)

Roy Debasis, Bagchi Biswajoy, Das Sukhen, Nandy Papiya
Physics Department, Jadavpur University Kolkata- 700 032. India

Keywords: Nanocomposite, Sol-gel methods, Scanning electron microscopy (SEM), X-ray diffraction (XRD), Electrical resistivity

Mullite composites have been synthesized at 400oC, 800oC, 1000oC and 1300oC via the sol-gel technique in the presence of cobalt. The electrical resistivity and activation energy of the composites have been measured and their variation with concentration of the metal ion doping has been investigated. The resistivity of doped mullite decreases rapidly from 400oC-800oC more gently from 1000oC-1300oC. The lowering of resistivity is due to the 3d orbital electrons and the concentration of cobalt ions. X-ray analysis confirms the presence of Co2+ ions in mullite, which entered the octahedral site. The Co2+ ion which substituted Al3+ ion in the octahedral site of mullite structure appeared to be efficient in reducing the resistivity. This has been confirmed due to the results of activation energy of resistivity/band gap energy, the Eg which was lowest for concentration 0.15 M. As the concentration increases, these ions lower the resistivity of mullite to a minimum.

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