Determining the percolation threshold for (FeCoZr)x(CaF2)(100−x) nanocomposites produced by pure argon ion-beam sputtering

Abstract

This study examines the frequency and temperature dependence of conductivity, phase shift angle and capacity of the (FeCoZr)x (CaF2)(100−x) nanocomposites, with the metal phase content in the range of 45 at.% < x < 90 at.%, produced by pure argon ion-beam sputtering. It was found that for the metallic phase content lower than 67 at.% there are temperature dependencies of the dielectric type of conductivity, for which the derivative dσ/dT > 0. Activation energy of conductivity, determined from the Arrhenius plot, is about ΔE ≈ 0.061 eV. For a metallic phase content above 67 at.%, the metallic type of conductivity occurs, for which the derivative dσ/dT < 0. At the frequency of 100 Hz and at liquid nitrogen temperature (LNT) a dependence of conductivity on the content of the metallic phase was shown. In the area of low metallic phase content a rapid increase of conductivity occurs (over six orders of magnitude) and temperature dependence exhibits the dielectric type of conduction. For higher contents of the metallic phase the metallic type of conductivity occurs, which decreases with increasing temperature. Based on the analysis of conductivity depending on the content of the metallic phase, the percolation threshold was determined for the (FeCoZr)x (CaF2)(100−x) nanocomposite, the value of which is xc ≈ (65.8 ± 2) at.%. It was agreed that in nanocomposites below the percolation threshold there are resonance phenomena of currents and voltages similar to the resonance phenomena in RLC circuits containing conventional inductance coils and capacitors.