Intermediate Phases And Reaction Kinetics Of The Furnace-Assisted Synthesis Of Sodium Tungsten Bronze Nanoparticles

The sodium tungsten bronzes are nonstoichiometric metal oxides which have recently attracted interest for their applications as plasmonic materials. Although several synthesis routes have been reported, none offer the flexibility and mass throughput of the furnace-assisted methods. Although widely used, the intermediate phases and kinetics of such methods have not previously been studied. In this work, we use in-situ neutron powder diffraction and Rietveld refinement to characterize sodium tungsten bronze synthesis, with a particular focus on preparing nanoparticles. The reaction is found to proceed much more quickly than previous ex-situ studies would suggest, as once the reagents reach the reaction temperature, phase purity is achieved within seconds. Through kinetic analysis, order-of-magnitude estimates for the Arrhenius parameters are obtained, and a two-step reaction mechanism is proposed. These findings contribute to the synthesis strategy of sodium tungsten bronze nanoparticles for plasmonic applications.