Na2Ti2Se9 was first discovered in the quaternary system Na/Ti/P/Se, but it can be prepared rationally by dissolving Ti in a Na2Sex flux at 375 °C. The silverish dark red crystals are air-and water-stable. A new method for synthesizing Na4TiSe4 is also reported. Na2Ti2Se9 crystallizes in space group P21 with a = 12.785(4), b = 14.848(4), c = 13.961(4) Å, β = 94.556(4)°, R1 = 0.0592 and wR2 = 0.1336. The structure is similar to that of K5NaTi6Se27. It contains infinite one dimensional chains which run parallel to the c-axis and contain Ti4+ centers bonded to Se22- and Se2- species. The 1/∞[Ti2(Se2)4Se]2- chains pack together in a hexagonal pattern. All of the titanium atoms are surrounded by a pentagonal bipyramid of selenium atoms. The selenium atoms bridge the Ti centers in two different ways. Na2Ti2Se9 is a semiconductor with a band gap, Eg, of ≃ 1.02 eV. The Raman spectra are also reported.
|Number of pages||8|
|Journal||Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences|
|Publication status||Published - Jan 2001|
- Molten salt fluxes
ASJC Scopus subject areas