Analysis of electrical conduction paths in Ni/YSZ participate composites using percolation theory

Abstract

Electrical conduction paths through the Ni phase in Ni/yttria-stabilized zirconia (YSZ) cermet heve been analyzed using a Monte Carlo simulation based on percolation theory and electrical conductivity measurement. The minimum Ni-volume fraction of total solids determined from the electrical conductivity measurement is 0.32. This value agrees with the percolation threshold, 0.324, determined for site percolation on a 36 × 36 × 36 simple cubic lattice. This confirms the fact that the site percolation model is effective for the electrical conduction of Ni/YSZ cermet. This simulation shows that at a 0.324 volume fraction of Ni, only 20% of the total Ni contributes to electrical conduction path formation; and at above a 0.44 volume fraction of Ni, at least 90% of the total Ni forms the electrical conduction paths. Moreover, the decrease with time in the electrical conductivity of the cermet is caused by the partial disconnection of the electrical conduction paths because of the sintering of Ni particles at high temperatures.