Structure and compositional trends in alkali-metal containing titanium and vanadium oxide chalcogenides and the new van der Waals phase Ti2Te2O

We report the solid-state synthesis of all eighteen layered oxide chalcogenides in the structural family AM2Q2 O (A = K/Rb/Cs; M = Ti/V; Q = S/Se/Te), allowing the determination of trends in composition and reactivity within the series. All materials are isostructural, crystallising in the primitive tetragonal space group P4/mmm as reported previously for five compounds in the series. The titanium or vanadium ions have intermediate valency on a single crystallographic site, leading to temperature-independent paramagnetism and correlated electronic behaviour which is influenced by the compositional variation. Furthermore, the alkali metal ions in and can be removed by oxidative deintercalation using at room temperature to produce a new metastable van der Waals layered phase, . During the deintercalation reaction the oxide chalcogenide layers undergo a relative shift by (0.5,0.5) in the ab plane such that is body-centered with space group I4/mmm.