Dynamics of the electric polarization and depolarization of graphite

The dynamics of direct-current-induced electric polarization/depolarization of a conductive material (graphite) are studied. Forward-current polarization and reverse-current depolarization cause the apparent resistivity to increase by ≤ 2.2% and ≤1.0%, respectively. Polarization-related carrier-atom interaction engagement occurs more readily than depolarization-related disengagement. The number n of carriers that participate increases with the number N_I of injected electrons; the rate of the n increase decreases with increasing N_I. The efficiency of carrier-atom interaction (indicated by n/N_I, ≤1.2 × 10⁻¹⁷) decreases with increasing N_I (≤1.2 × 10²⁰). For the same N_I, the fraction of carriers that participate (n/(N_I + N_c), where N_c = number of inherent carriers) increases with increasing current (rate of electron injection). At a particular current, this fraction increases and then decreases with increasing N_I. The polarization/depolarization rate decreases as polarization/depolarization proceeds. At a given polarization/depolarization time, the rate and degree of polarization are higher than those of depolarization. The above fraction is higher for polarization (≤8.5 × 10⁻¹⁸) than depolarization (≤4.7 × 10⁻¹⁸). The difference between polarization and depolarization agrees with the apparent-resistivity asymmetry and true electret character indicated by the open-circuited DC electric field of 1.0 × 10⁻⁵ V/m. The above fraction is lower than the fraction of carriers that participate in the electret discharge (4.9 × 10⁻⁴) by 14 orders of magnitude.