Doping‐induced‐effects on conduction mechanisms in incommensurate ammonium zinc chloride crystals

Abstract

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 Mn 2+ in different concentrations changed strongly both values of σ at all temperatures and the dependence of ln σ dc 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 (NH 4 ) 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 Mn 2+ -content on values of µ, ϕ and β RS in different phases of AZC was also considered.

Tailoring charge transport in epoxy based composite under temperature gradient using K2Ti6O13 and asbestine whiskers

“…However, the impurities introduced in the manufacturing process of dielectrics inevitably bring high energy levels to the band gap. Based on the Schottky effects, charges trapped in the impurity energy levels can be stimulated either by electric forces or under high temperatures [50,51]. In addition, electrons can transfer through the dielectrics by hopping mechanism, when they obtain sufficient energy from external stimulation [52].…”