Abstract
We substantiate the mechanism of electrical conductivity of powder consisting of dielectric nanoparticles with ionized donor centers on the surface and free electrons in the bulk. It is shown that in a powder switched to a closed dc circuit, the electric field strength vanishes due to the polarization of the powder by the source of the electromotive force. The Ohmic loss becomes impossible. The electrons of the polarized powder are in the states that correspond to the minimum of the powder energy and zero Ohmic resistance. The fulfillment of these conditions does not depend on the temperature (T = 300-500 K) and the strength of the circuit current. The electric current in the powder is maintained on account of the difference in the electrochemical potentials of electrodes that are in contact with the polarized powder.