Niobium oxyiodide clusters from heterogeneous solid-state reactions: the example of Li3Nb7O5I14(NbI6)

Abstract

No fewer than nine niobium oxyiodide phases have been synthesised and characterised from the reaction between NbI₄ and Li₂O in the presence of Li₂(CN₂) under closed-system conditions at temperatures between 400 °C and 500 °C. Reactions in this system proceed through diffusion-controlled solid–solid pathways as well as gas-phase reactions that extend beyond equilibrium, which enables the concurrent formation of multiple niobium oxyiodide compounds. The crystal structures of these products display a range of architectures based on different niobium oxide clusters, including the [Nb₇O₅] core, which is a characteristic structural motif in the structure of Li₃Nb₇O₅I₁₄(NbI₆), the compound examined in this report.