New Chemical Reaction Process of a Bi2Te2.7Se0.3 Nanomaterial for Feasible Optimization in Transport Properties Resulting in Predominant n‑Type Thermoelectric Performance

Various chemical reaction processes have been adopted to synthesize Bi2Te3 thermoelectric nanomaterials for achieving remarkably low thermal conductivities, but chemical contaminations were usually pointed out as flaws, severely deteriorating electrical conductivities. We devised a novel water-based chemical reaction process for a Bi2Te2.7Se0.3 nanocompound in which the possibility for chemical contaminations was reduced. We successfully synthesized a small and highly distributed Bi2Te2.7Se0.3 nanocompound with high purity and adequately packed it via a spark plasma sintering process to produce a nanobulk structure. The resulting nanobulk specimen exhibited a physical density as high as the theoretical one with highly distributed nanograins; thus, we were able to obtain remarkably high electrical conductivity while maintaining thermal conductivity as low as possible. The synergistic effect was greatly induced between the transport properties; thus, the highest reported figure of merit value was achieved for n-type Bi2Te3 in the bulk phase.