The dc conductivity (σ) along the polar b-axis of ammonium zinc chloride (AZC) crystals in its four hightemperature
phases has been measured as a function of temperature. Doping with Mn2+ in different
concentrations changed strongly both values of σ at all temperatures and the dependence of ln σdc on 1/T in
the phase transition regions. The activation energy of conduction was calculated from the linear portions of
this dependence in each phase. The results were discussed in the light of the decomposition of (NH4)2 in the
high-temperature normal phase, the discommensuaration (DC) formation/annihilation in the incommensurate
phase and domain wall motion and stripples nucleation in the commensurate- and antiferroelectric-phases.
Pinning of DC’s in the crystal lattice and/or by the structural defects and the possibility of dislocation
formation was also discussed. The bulk- and the electrode-limited conduction mechanisms were also
considered. The current density-voltage gradient relationship according to the usual Richardson-Schottky (RS)
equation shows disagreement between extracted parameters and experimentally measured ones. A
modified equation was used to solve this difficulty which, in addition, facilitated the calculation of the
electronic mobility (μ), the barrier height (ϕ) at the electrode-dielectric interface and the R-S constant (βRS).
The effect of Mn2+-content on values of μ, ϕ and βRS in different phases of AZC was also considered