Solution Synthesis and Diffusion-Mediated Formation Pathway of NbTe 4 Particles.

NbTe 4 is 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 NbTe 4 is typically synthesized through high-temperature solid-state or metal flux reactions and NbTe 4 films can be made by sputtering and annealing, but NbTe 4 is generally not amenable to the lower-temperature solution-based syntheses that yield small particles. Here, we demonstrate a solvothermal route to NbTe 4 particles that is based on mainstream colloidal nanoparticle synthesis. We find that the reaction proceeds in situ through a multistep pathway that begins by first forming elemental tellurium needles. NbTe 4 then 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 NbTe 4 define how the diffusion-based reaction proceeds and help to rationalize the morphology of the resulting NbTe 4 particles. As synthesized, NbTe 4 particles exhibit a surface consisting of predominantly Nb-Te and reduced NbO x species, but after storage, surface oxidation transforms these species to primarily Nb 2 O 5 and TeO 2 , while the NbTe 4 remains unchanged. These synthetic capabilities and reaction pathway insights for NbTe 4 , made using a solvothermal method, will help to advance future studies on the properties and applications of this and related tellurides.