Electrical-conductivity and Hall-effect measurements in semiconducting powders. Study of percolation effects

We report Hall and conductivity measurements on ZnO-ZnS powder mixtures over the range (25-100)-wt.% ZnO. The conductivity shows "classical" percolation behavior according to the equation σ=σ₀(X-Xc)ˢ where X is the volume fraction of ZnO. The values of Xc and S are found to be Xc=0.135±0.020 and S=1.7±0.2. Though there is considerable scatter in the Hall coefficient, it remains approximately constant over the range of the measurements. This is reflected in the fact that we obtain the same exponent S from a plot of Hall mobility versus X-Xc as is given by the conductivity.