Improved Thermoelectric Performance of Eco‐Friendly β‐FeSi2–SiGe Nanocomposite via Synergistic Hierarchical Structuring,Phase Percolation,and Selective Doping

A β‐FeSi₂–SiGe nanocomposite is synthesized via a react/transform spark plasma sintering technique, in which eutectoid phase transformation, Ge alloying, selective doping, and sintering are completed in a single process, resulting in a greatly reduced process time and thermal budget. Hierarchical structuring of the SiGe secondary phase to achieve coexistence of a percolated network with isolated nanoscale inclusions effectively decouples the thermal and electrical transport. Combined with selective doping that reduces conduction band offsets, the percolation strategy produces overall electron mobilities 30 times higher than those of similar materials produced using typical powder‐processing routes. As a result, a maximum thermoelectric figure of merit ZT of ≈0.7 at 700 °C is achieved in the β‐FeSi₂–SiGe nanocomposite.