Synthesis and characterization of the pseudo-hexagonal hollandites ALi2Ru6O12 (A=Na, K)

The crystal structures, synthesis and physical properties of ruthenium hollandites ALi2Ru6O12 (A=Na, K) with a new pseudo-hexagonal structure type are described. Analogous to tetragonal hollandites, the framework is made of MO6 octahedra in double chains that share corner oxygens with each other to create interstitial tunnels. The tunnels are either hexagonal or triangular in cross-section. Magnetic susceptibilities, low temperature specific heat, and electrical resistivities are reported. The data indicate that these materials are normal, low density of states metals. This new structure type can be extended from A=Group I to A=Group II ions with the synthesis of CaLi2Ru6O12 and SrLi2Ru6O12.

Graphical abstractThe crystal structure of NaLi2Ru6O12 with emphasis on the RuO6 octahedra (cyan). Na (magenta) and Li ions (blue) are located in hexagonal and triangular channels, respectively. This new hollandite structure type has pseudo-hexagonal symmetry.Figure optionsDownload full-size imageDownload as PowerPoint slide