In the same way metal complexes are converted into well-defined nanoparticles, nanoparticles can be used as tunable precursors capable of evolving into macroscopic solids with specific structural features. A consolidation step is usually required to produce the macroscopic solid from nanoparticles. The consolidation process defines the density and microstructure of the solids, which directly correlate with the electronic, thermal, and mechanical properties of the resulting material. In order to provide the material with densities as close as possible to the respective theoretical density, pressure-assisted sintering techniques are preferred, such as hot pressing or spark plasma sintering.

Characteristics of the particles such as size, shape, composition, and surface chemistry determine the sintering process and therefore dictate densification, grain growth, and materials' final microstructure. Consequently, using carefully-curated nanoparticles provides a unique opportunity to control material microstructure. In our framework, a nanoparticle is a multi-structured system consisting of an inorganic nanocrystalline domain, named the inorganic core, surrounded by surface species. Both the inorganic and surface species are tunable parameters in the design of nanoparticle-based precursors. Herein, we will employ solution-based synthesis procedures to produce precisely defined nanoparticles and explore their surface chemistry to adjust nanoparticles' reactivity during sintering to achieve a solid with specific targeted features.

Two very different approaches to controlling particles' surface chemistry need to be separated. One refers to the particle termination atoms, the other to the connected adsorbates that can be covalently bonded molecules or electrostatically adsorbed ionic groups. In this talk, we will show how surface adsorbates, intentionally or unintentionally introduced, are critical to controlling densification, grain growth, and materials' final microstructure. Furthermore, we will present different surface functionalization strategies that allow defining: atomic defects, grain boundary complexions, crystalline domain size, and the formation of secondary phase inclusions in the macroscopic solid.

Finally, we will discuss the effect of the different structural properties introduced in the macroscopic solids on their electrical and thermal transport properties and evaluate their potential as thermoelectric materials.