The dc conductivity (σ) along the polar b-axis of ammonium zinc chloride (AZC) crystals in its four high-temperature 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 σ 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 (R-S) 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 (β_RS). The effect of Mn²⁺-content on values of μ, φ and β_RS in different phases of AZC was also considered.

---

If you have come directly to this page, click this symbol to go to the CRT homepage.

The full text of this paper in pdf-Format is available at Wiley Interscience.