Processing, Resistivity and Microstructure of Al-Kaolinite Clay-Based Cermet System

  • S.G. Ayodele Department of Physics University of Ilorin P.M.B. 1515, Ilorin. Nigeria
  • T. Akomolafe Department of Physics University of Ilorin P.M.B. 1515, Ilorin. Nigeria
Keywords: Annealing, Composite materials, Electrical conductivity, Electron microscopy, Resistors, Sintering


Cermets have been fabricated from naturally occurring Al-clay based admixtures. The effect of processing parameters such as firing temperature, firing time and furnace atmosphere on the electrical conductivity and microstructure of the cermets were investigated. Our electrical measurements reveal that the electrical properties vary remarkably with the annealing schedule. The resistance decreases with increasing peak firing temperature TF, being very rapid at the early stage of firing, i.e between 300 oC and 700 oC. All the cermets have negative temperature coefficient of resistance (TCR) with the magnitude of the TCR dropping from 1220 ppm/oC at peak firing temperature TF of 200 oC to as low as 50 ppm/oC for TF =1000 oC. The range of the TCR obtained is comparable to that reported for some thermistors, varistors and other standard resistors. Observations of the microstructure by Scanning Electron Microscope (SEM) showed that increasing the peak firing temperature TF enhances sintering of the conducting grains. X-ray diffraction (XRD) analysis indicates kaolinite as the major mineral in the clay. An optimum peak firing temperature of 700 oC is recommended for these cermets based on the criteria of low resistivity, low bulk density and stable microstructure of the cermets.

Author Biographies

S.G. Ayodele, Department of Physics University of Ilorin P.M.B. 1515, Ilorin. Nigeria

Department of Physics
University of Ilorin
P.M.B. 1515, Ilorin. Nigeria

T. Akomolafe, Department of Physics University of Ilorin P.M.B. 1515, Ilorin. Nigeria

Department of Physics
University of Ilorin
P.M.B. 1515, Ilorin. Nigeria


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How to Cite
Ayodele, S., & Akomolafe, T. (2008). Processing, Resistivity and Microstructure of Al-Kaolinite Clay-Based Cermet System. Ife Journal of Technology, 17(1), 23-29. Retrieved from