Ionic Conductivity

Ionic conductivity in tysonite-type solid solutions La1−xBaxF3−x

“…The ideal solution approximation, which ignores coulombie interactions between defects, is formally not applicable for moderate dopant concentrations (x > 1 X 10-3). The degree of association can be lowered by taking into account interactions between the free defect (VF), and its surrounding charge-cloud, the so-called Debye-H~ickel-Lidiard (DHL) theory [30]. The reduction of the association enthalpy can then be interpreted as a change-over from conductivity in the association region at low doping concentrations to a new free-defect conductivity in the concentrated region.…”

Electrical conductivity in NH4Cl and ND4Cl single crystals

“…The equation for the conductivity can be written as where N a and N c are the numbers of anion and cation vacancies per unit volume and where μ a and μ c are the anion and cation mobilities. The equations for the vacancy concentrations and ion mobilities are well known [5], and in our notation are:…”

“…On the other hand, barring the unlikely coincidence of equal activation energies, a linear Arrhenius plot would indicate that one charge carrier predominates and that the conductivity can be expressed as a single exponential, This appears to be the situation for NH 4 Cl. According to classical rate theory, the jump attempt frequency is proportional to the inverse square root of the mass of the vibrating ion [5]. In the case of NH 4 Cl and ND 4 Cl this means that if the mechanism for conduction is the motion of the anions, the conductivity of NH 4 Cl and ND 4 Cl would be the same; if the mechanism is cation motion, the ratio of NH 4 Cl conductivity to ND 4 Cl conductivity would be √¯1¯1¯/¯9; if the mechanism for conduction is dominated by motion of a hydrogen ion, then the above ratio takes on the value √¯2.…”

Bulk conductivity and polarization of ionic crystals exhibiting defect exchange between inequivalent sites

“…Elementary treatments of the ionic conductivity of solids [1,2] usually include a derivation of the bulk conductivity for materials in which the motion of each charge-carrying species is governed by a single, thermally activated, jump probability. In crystals with moderately complex lattice structures, however, the motion of a given defect species may involve several distinguishable jump processes, each governed by a different activation enthalpy.…”

“…In connection with recent experimental studies of the small-signal ac response of LaF 3 [3,4], the present authors have developed a generalization of the previous simple theory [1,2], which takes into account the existence of several different possible jump processes for anion vacancies in materials of the tysonite structure. Our treatment leads to a number of interesting predictions which should also apply to some other groups of ionically conducting solids.…”