| dc.description.abstract | Thermoelectric generators, solid-state devices that convert heat into electricity, exhibit desirable characteristics such as low maintenance costs and excellent reliability that make them indispensable to any future portfolio of clean energy technologies. Nevertheless, the low conversion efficiencies of these generators mean that deployment significantly lags behind that of other renewable energy technologies such as solar. Thermoelectric power generation efficiency is primarily limited by a material-dependent parameter called the dimensionless figure of merit, zT, which is directly dependent on the materials’ Seebeck coefficients, electrical, and thermal conductivities. Complex relationships between these parameters make enhancing zT values of materials challenging. Another problem with current thermoelectric modules is that they are composed of toxic and rare-earth elements. Therefore, a need exists for enhancing zT values of materials that are solely composed of earth-abundant and non-toxic elements. A material that fits the above-mentioned description is magnesium silicide stannide, a pseudobinary alloy. Unlike magnesium silicide, compositional variation serves as the first tunable parameter in altering the zT values of this material. Another lever for tuning the zT values of this alloy is morphology variation via nanostructuring (e.g., nanowires). As individual nanowires are ill-suited for commercial production of thermoelectrics based on magnesium silicide stannide, properties of bulk nanowire assemblies must be studied and optimized. However, despite theoretical evidence for reduced thermal conductivity in magnesium silicide stannide nanowires relative to bulk, there have been no experimental studies on this topic. Consequently, the primary objective of the present work was to demonstrate the synthesis, processing, and characterization of magnesium silicide stannide nanowires of different diameters and elucidate the effect of intentional nanostructuring and size variations on the thermal conductivity of the material. More specifically, pre-synthesized silicon nanowires and bulk magnesium stannide were employed as starting materials for the solid-state synthesis of magnesium silicide stannide. Variation of the diameters of the silicon nanowires allowed for varying the ultimate diameters of alloy nanowires. Finally, bulk assemblies of magnesium silicide stannide nanowires, obtained via uniaxial hot pressing, indicated that nanowire diameter reduction is an effective strategy for reducing thermal conductivity of the material. | en |
