Synthesis and Characterization of Cs_1-xTi₂Te₂O (x ≈ 0.2): Electron Doping by Te Resulting in a Layered Metal

Reacting Cs₂O_1.3, TiTe, TiO₂, and Te under inert conditions gives powders of Cs_1-xTi₂Te₂O (x ≈ 0.2). Small single crystals of the same phase were obtained from a CsCl salt melt in closed ampoules. This cesium dititanium ditelluride oxide (P4/mmm, a = 4.0934(3) Å, c = 8.9504(9) Å) is isostructural to CeCr₂Si₂C and contains layers of face-sharing trans-TiTe₄O₂ octahedra that are separated by Cs. As Ti occupies only one crystallographic site, its average oxidation state is +2.6, for the Cs deficit x = 0.2. The formally intermediate Ti valence state agrees well with the metallic conductivity and temperature-independent paramagnetic behavior. No superconductivity is observed down to 0.1 K in Cs_0.8Ti₂Te₂O, but the fact that this structure type can accommodate Te^2- suggests that electron doping of structurally closely related pnictide oxide superconductors, for example, BaTi₂Bi₂O, might be possible.