Localization of charge carriers in materials with high polaron concentration

The influence of polaron concentration on the type of transition from band to activate conductivity has been investigated. For a single polaron in the crystal lattice or for material with polaron concentration higher than the percolation threshold, such a transition is continuous, in accordance with theory. However, for intermediate cases this process becomes step-like, because the rapid increase of density of states at Fermi level leads to a change of polaron characteristics. These suppositions are illustrated by experimental results (XPS-spectra, crystal structure analysis, DC conductivity) for intercalation compounds based on titanium dichalcogenides