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)