Abnormal dielectric relaxation phenomena in mixture of polar liquid and conductive particles

Dielectric measurements of water and methanol containing gold, graphite, silicon, silicon carbide, and silicon nitride powders were performed using the time domain reflectometry method. The relaxation process caused by orientation of the polar liquid molecules was observed in the frequency range of 100 MHz to 20 GHz, similar to the pure liquid. The relaxation strength shows an abnormal increase with volume fraction growth of the conductor or semiconductor, and it diverged at a certain fraction. The dependence on the concentration of Δε_app is experimentally given by Δε_app=δγΔε_L/(Φ_L-1+γ)+(1-δ)Φ_LΔε_L, where Φ_L is the volume fraction of the liquid, Δε_L is the relaxation strength of the liquid, δ is the weighting parameter of the first term for the conductor property and the second term for the insulator property, and γ is a constant which expresses the degree of the shielding effect versus the applied electric field by the conductive particles. A divergence of Δε_app at Φ_L=1-γ shown in the experimental results can be expected by this equation. This equation also expresses the properties of silicon carbide, which has a low conductivity, and also the insulator silicon nitride. These new findings in dielectric characteristics are applicable to a wide number of industrial purposes. © 2002 American Institute of Physics.