Reaction-Assisted Hierarchical Structuring for Enhanced Thermoelectric Performance in BiSbTe via In Situ Decomposition of GdCo2 Precursors.

Integrating functional nanoparticles into thermoelectric matrices is a widely used strategy for performance optimization. However, the thermodynamic instability of such inclusions during high-temperature sintering frequently triggers interfacial reactions that degrade expected functionality. Traditionally, these reactions are regarded as detrimental and are suppressed through complex surface modification processes. This work breaks through this convention by proposing a reaction-assisted nanocompositing strategy, in which the in situ chemical reaction between GdCo2 nanoparticles and p-type BiSbTe matrix is utilized as a spontaneous route for hierarchical microstructure construction. Instead of maintaining the initial magnetic phase, GdCo2 precursors undergo decomposition during spark plasma sintering, playing a dual role: released Co atoms intercalate into the van der Waals gaps of BiSbTe to finely tune carrier concentration, while residual species self-assemble into nanoscale CoTe2 precipitates and Gd-rich clusters. These reaction-induced structures act as efficient multiscale phonon scattering centers, reducing lattice thermal conductivity by ∼16.3% while preserving high carrier mobility. As a result, the optimized composite with 0.35 wt % GdCo2 achieves a peak zT value of ∼1.30 at 350 K. This study provides a universal and reliable design principle for improving thermoelectric performance by converting interfacial instability from a disadvantage into an effective regulation strategy for thermoelectric performance enhancement.