On the effective Leontovich boundary conditions for polycrystals

Under the conditions of the normal skin-effect the effective surface impedance of a polycrystalline metal has been calculated assuming that the penetration depth of the electromagnetic field is small com[pared with the mean size of a polycrystal grain. By proceeding from the local Leontovich boundary conditions it has been shown that for an arbitrary anisotropy of the conductivity tensor of the single crystal grains out of which the polycrystal is composed, the elements of effective impedance are equal to the averages of the single crystal impedance tensor over all possible rotations of the crystallite. It should be noted that in spite of surface impedance being the surface resistivity of a homogeneous metal, the effective impedance of a polycrystal (or, generally, of an inhomogeneous metal) is not equal to its effective two-dimensional resistivity.