Solid state studies on K<inf>2</inf>Ti<inf>6-x</inf>Nb<inf>x</inf>Fe <inf>2</inf>O<inf>16</inf> (x = 0 and 1) and lithium insertion into K <inf>2</inf>Ti<inf>6</inf>M<inf>2</inf>O<inf>16</inf> (M = Cr, Fe and Ga) and K<inf>2</inf>Ti<inf>5</inf>NbFe<inf>2</inf>O<inf>16</inf> hollandite type phases

A new niobium-substituted hollandite K2Ti5NbFe 2O16 has been synthesised for the first time. The compound is crystallised in tetragonal structure. A two to three orders change in electrical resistivity is observed with temperature as compared to the parent phase K2Ti6Fe2O16. The niobium-substituted phase shows antiferromagnetic ordering with TN = 37K at a field of 0.1T and the antiferromagnetic ordering disappears at higher field (0.2T) indicating field induced magnetic behaviour. The Mössbauer spectrum of K2Ti5NbFe2O16 shows majority of the Fe ions are 3+ oxidation state (96%). For the first time, we have intercalated lithium into K2Ti6M2O 16 (M = Cr, Fe and Ga) and K2Ti5NbFe 2O16 hollandite type phases using n-butyllithium in hexane. The estimated lithium content for all the phases are in the range 1.7-2.7mol per formula unit. © 2003 Elsevier B.V. All rights reserved.