Ordering of an intercalated impurity near the temperature of polaron band collapse in AgxTiTe2

The phase diagram of an AgxTiTe2 intercalation compound near the temperatur e of polaron band collapse is studied by x-ray structure analysis. The resu lts obtained confirm the assumption made earlier that, at temperatures clos e to the polaron band collapse point, a homogeneous state cannot exist in t he charge carrier concentration range in which the Fermi level lies between the bottom and the center of an impurity band. The reversible transition a ccompanied by ordering of intercalated silver is revealed upon heating to a temperature close to the polaron band collapse point. This transition is e xplained by the enhancement of Coulomb repulsion between impurity atoms due to the localization of charge carriers. (C) 2001 MAIK "Nauka/Interperiodic a".