Electrical conductivity of an alumina matrix and FeAl particles composites

Different amounts of FeAl (from 5 to 35 vol.%) were added to Al/sub 2/O/sub 3/ matrices and the resulting mixtures were hot-pressed to produce dense metal toughened-ceramic composites. Their electrical properties were measured using two-probe impedance spectroscopy within the 5 Hz - 13 MHz frequency range and the 25 degrees C-1000 degrees C temperature range. We find that the electrical behavior of these composites is dominated by a percolation mechanism. Due to the percolation effect, a sharp increase in the electrical conductivity of the composites is observed at FeAl fractions higher than 25%. The experimental data were fitted by the GEM equation which, by taking into account the intrinsic conductivity and geometry of both components, gives information on how the volume fraction and shape of the embedded particles affects the overall composite conductivity. Our results prove that the conductivity of these metal toughened-ceramic composites is strongly affected by the amount and less by the size of the metal particles. (10 References).