Dielectric Enhancement from Non-Insulating Particles with Ideally Polarized Interfaces and Zero zeta-Potential I: Exact Solution

We solve exactly the dielectric response of a non-insulating sphere of radius a suspended in an electrolyte solution, with ideally-polarizable interface but without signicant zeta-potential. We then use this solution to derive the dielectric response of a dilute random suspension of such spheres, with volume fraction f << 1, within the Maxwell-Garnett Eective Medium Approximation. Surprisingly, we discover a huge dielectric enhancement in this bare essential model of dielectric responses of solids in electrolyte solution: at low frequency ,
the real part of the eective dielectric constant of the mixture is 1 -(3f/2) + (9f/4)(a/λ). Here λ is the Debye screening length in the solution. As λ is of the order nm even for dilute electrolyte solution, even for sub-mm spheres and low volume fraction f = 0:05 the huge geometric factor a/λ implies an over 10⁴-fold enhancement. We provide a physical picture of the enhancement from an accumulation of charges in a thin Externally Induced Double Layer(EIDL) due to the blocking boundary condition on interfaces. This mechanism is distinct from the traditional dielectric enhancement in insulating particles due to large intrinsic zeta -potentials. Our predictions compare favoably with the preliminary laboratory data (unpublished).