Synthesis and physical properties of the hollandite‐type titanium oxide KxTi8O16

Polycrystalline sample of hollandite-type titanium oxide KxTi8O16 has been prepared and studied by magnetization and X-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behaviour is observed in the magnetic hysteresis measurements. XPS measurements of the Ti 2p3/2 core-level finds that the titanium ions take a mixed valence of Ti4+ and Ti3+. In addition, the valence band spectrum reveals that the 3d electrons tend to local-ize on Ti3+ ions in the hollandite-type TiO2 lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type KxTi8O16 sample can be classified as a TiO2-based wide-gap semiconductor with Curie temperature above room temperature (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)