Solution Synthesis and Diffusion-Mediated Formation Pathway of NbTe4Particles

NbTe4is an important material because of its fundamental low-temperature electronic behavior and its potential interest for thermoelectric, catalytic, and phase-change applications, especially as nano- and microscale particles. As a tellurium-rich group V transition metal telluride, bulk NbTe4is typically synthesized through high-temperature solid-state or metal flux reactions and NbTe4films can be made by sputtering and annealing, but NbTe4is generally not amenable to the lower-temperature solution-based syntheses that yield small particles. Here, we demonstrate a solvothermal route to NbTe4particles that is based on mainstream colloidal nanoparticle synthesis. We find that the reaction proceeds in situthrough a multistep pathway that begins by first forming elemental tellurium needles. NbTe4then deposits on the surface of the tellurium needles through a diffusion-based process. Time-point studies throughout the reaction reveal that crystallographic relationships between Te and NbTe4define how the diffusion-based reaction proceeds and help to rationalize the morphology of the resulting NbTe4particles. As synthesized, NbTe4particles exhibit a surface consisting of predominantly Nb–Te and reduced NbOxspecies, but after storage, surface oxidation transforms these species to primarily Nb2O5and TeO2, while the NbTe4remains unchanged. These synthetic capabilities and reaction pathway insights for NbTe4, made using a solvothermal method, will help to advance future studies on the properties and applications of this and related tellurides.