Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The ac electrical conductivity and anisotropy, including an evaluation of the dielectric constant, at 10<jats:sup>8</jats:sup> and 2 × 10<jats:sup>8</jats:sup> Hz in the range 77 to 350°K is investigated. A hopping mechanism is evidenced from the dispersion of conductivity observed below 200°K, and is associated with the existence of tails of localized states at the edges of a band gap. The vanishing dispersion in the upper temperature range is likely to indicate that an interband transition process may then become important for conduction.</jats:p>