Ag-TiTe2 phase diagram and electrical properties of silver-intercalated titanium ditelluride

Phase-diagram studies of AgxTiTe2 intercalation compounds indicate the existence of three phases designated as Ag1/2TiTe2 (0.55 < x < 0.57 at 470 K, sp. gr. P2/m), Ag3/4TiTe2 (0.65 < x < 0.75, sp. gr. <P(3)over bar> m1), and AgTiTe2 (0.95 < x < 1.0, sp. gr. <P(3)over bar> m1). The structures of the three phases result from two-dimensional ordering of silver ions in the van der Waals gaps. The thermoelectric power and de conductivity of Ag1/2TiTe2 and Ag3/4TiTe2 are measured. The results are interpreted under the assumption that a band of localized states is formed in Ag1/2TiTe2 near the Fermi level; upon a further increase in silver content, electrons occupy this band, and as a result the material exhibits metallic conductivity. Between 400 and 420 K, Ag3/4TiTe2 undergoes a metal-semiconductor transition, which is tentatively attributed to partial disordering in the silver sublattice.