Details

Autor(en) / Beteiligte

• AYODELE, S. G
• AKOMOLAFE, T

Titel

Dc electrical properties and conduction mechanisms of Al-clay based composite resistors

Ist Teil von

• Journal of materials science, 2005-12, Vol.40 (23), p.6131-6138

Ort / Verlag

Heidelberg: Springer

Erscheinungsjahr

2005

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The electrical properties of composite resistors fabricated from materials of natural origin based on Al-kaolinite clay mixture were studied. Electrical measurements and microstructural studies showed the effect of the annealing schedule, insulating particle size and composition on the resistance of the cermet. Small values of activation energy of conduction from temperature dependence of resistance were measured and compared with those obtained from microstructural examinations using electron microscopy. The small activation energy in the range 0.53-1.24 microeV obtained suggests conduction by direct or quantum mechanical tunnelling between conducting grains. All the resistors were observed to show a negative TCR with some possessing TCR as low as 50 ppm/C in magnitude, which further confirms the tunnelling conduction process. The variation of resistivity with the volume fraction of the metallic phase followed a percolative conduction expression of the form R(X) = RM(x-xc) exp(-t), with the critical exponent t and critical concentration xc showing a significant dependence on firing temperature. It was found that the critical exponent assumed a value of t = 2.0 plus or minus 0.8, which is different from a universal value of 2.0. This was shown to result from the tunnelling-percolating nature of the cermet.