Thermophysical Assessments on Self-Assembled Tellurium Nanostructures

Abstract

Thermal properties of self-assembled nanostructures are of great importance to explain the structural phase transformation phenomenon. We report on the thermophysical assessments on tellurium nanostructures (TeN) that have been prepared using a facile wet-chemical technique by admixing precursor sodium telluride (Na 2 TeO 3 ) and sodium molybdate (Na 2 MoO 4 ) catalysts in hydrazine hydrate solution and heated at 120 °C, over 5−7 h. The extracted products (interval: 0.5 h) were subjected to a number of spectromicroscopic techniques including thermal measurements. Under identical growth conditions, the morphology of TeN was found to be transformed from Te nanotube (TT) to Te nanoflake (TF) at 6 h. Analysis revealed that Mo participated actively during 6 h of growth time, thereby making bonds with oxygen and the Te host lattice. At the vicinity of the phase transformation, Mo acquired an interstitial position in the hexagonal motif due to enhancement in catalytic efficiency that led to the formation of MoO 2 − moieties, which transiently reacted with host lattices resulting in surface charging of the tubes. This, in turn, created the coalescing effect with neighboring colloidal tubes through the van der Waals interaction. Thermal properties such as thermal conductivity, effusivity, diffusivity, and specific heat studied for TeN showed prominent surface effects. The increased surface area and enhanced amount of polycrystallinity resulted in unprecedently low thermal properties of TF due to severe phonon confinement.