Narrow Results

The effect of metal particles (Mo) inclusion in an insulating matrix (Al₂O₃) has been investigated. The conducting phase (Mo) is dispersed in alumina in different amounts (00%, 5%, 10%, 20%, 25% in volume). Two types of Mo particles have been used: the first with an average particle size ≅0.56 μm, the other with an average particle size ≅10.0 μm. All specimens were fabricated by hot pressing. The bulk conductivities have been measured over temperatures ranging from 500°C to 900°C using two-probe impedance spectroscopy within the available frequency range (5 Hz–13 MHz). From the interpretation of the impedance spectra, it has been observed that the bulk conductivity for fine particles of Mo inclusion in alumina is higher than that for large particles of Mo inclusion in alumina. A microstructural study revealed that below 15 vol% of Mo inclusion in Al₂O₃ samples had no-contact random patterns. Samples with metal contents higher than 20 vol% of Mo consistently showed metallic conductivity due to percolation effect.