Abstract
Growing process of the clusters in a composite consisting of niobium(Nb) and alumina(Al2O3), which was fabricated by hot-pressing under a uniaxial pressure, has been investigated with particular reference to the structural anisotropy and its effect on the percolative behavior of the electric conductivity σ. The percolation transition occurs at the critical volume fraction of Nb phase, fc=0.154 or fc=0.185, depending on the spatial direction. The conductivity obeys the critical power law with a universal exponent t≈2 after the transition. The statistic behavior of the structural anisotropy was measured with the aid of an image processor. The relationship between this structural anisotropy and the directional anisotropy of σ is well explained by developing the link-node-blob model. The result indicates that the sintered media like the above composite realize a percolation system virtually equivalent to the discrete percolation system produced on the lattice.
