A percolation treatment of the conductivity for the high-temperature small-polaron hopping regime in disordered systems

On the Electrical Conductivity of PrREBaCuO (RE = Er, Yb, Lu, Tm): Compounds in Orthorhombic Phase

“…This is witnessed by the temperature dependence of the conductivity which is of polaron-hopping type. Complementary to this, the experimental ratios In o,/ln oj of the conductivity, for different temperatures T, =k T,, were in very good agreement with Triberis and Friedman's [5] This was expected because the non-stoichiometry of GdBa,Cu,O, as well as of Gd,,,RE,,,Ba,Cu,O,-, (RE = Y, Sm, Eu, and La) introduces disorder in the system [7] and, together with the random arrangement of the constituents, allows us to conclude that the conductivity is dominated by thermally activated hopping of small polarons.…”

“…For high temperatures the agreement with Triberis and Friedman's model [5], presented in Section 3, which predicts a (7;./TJ215 ratio is very satisfactory. This law does not fit well enough for temperatures lower than 60 K, where we have a very good agreement using (6) which is valid at low temperatures and predicts (T/TJ114 ratios.…”

“…The generalized molecular crystal model (GMCM) used for the study of the small-polaron hopping motion in a disordered system has already been described in some detail by Triberis and Friedman [5] and Triberis [18, 191. Here, we describe it in brief.…”

“…Based on this model and using percolation-theoretic considerations, Triberis and Friedman [5], and Triberis et al [6], evaluated the dc conductivity of a disordered material, for high and low temperatures, respectively.…”

“…In the present work we present experimental results obtained by direct measurement of the dc conductivity of a variety of Pr-RE-Ba-Cu-0 (RE = Er, Yb, Lu, and Tm) compounds and we analyse the transport mechanism using the small-polaron hopping models proposed by Triberis and Friedman [5] and Triberis et al [6].…”