Experimental and theoretical studies were, conducted on the effect of particle size, packing fraction and surface modification of particles on the measurement of contact potential difference between a powder bed and a metal. It was found that the absolute value of the contact potential difference increases with decreasing particle size. The potential where the current detected becomes null, changes with the packing fraction of particles and tends to be constant at high packing fraction. These results are explained by introducing the effective surface area of charge transfer in the previous analysis.
The contact potential difference changes with the surface modification of particles due to stearic acid. The value tends to be the contact potential difference between stearic acid and the gold electrode as the film thickness of stearic acid becomes greater than about 0.03μm. The experimental results are well explained based on Poisson's equation near the interface of the particle and stearic acid.