Magnéli phases TinO2n−1 nanowires: Formation, optical, and transport properties

We have prepared triclinic Ti8O15 nanowires and Ti4O7 quasi-one-dimensional fibers by heat-treating thick H2Ti3O7 nanowires under hydrogen atmospheres at 850 and 1050°C, respectively. In contrast to wide-bandgap semiconducting tetragonal TiO2, both Ti8O15 and Ti4O7 exhibit high electrical conducting behavior at room temperature. The electrical conductivities of Ti8O15 and Ti4O7 are, respectively, 0.24 and 10.4S∕cm at 300K, and 2.4×10−5 and 4×10−3S∕cm at 77K. In both materials, the light absorption band covers the full visible-light spectrum region and extends into the near-infrared region.