High-entropy chalcogenides (HECs) such as (SnPbGeSiSb)Se3 have emerged as a groundbreaking class of materials for thermoelectric applications due to their exceptional configurational entropy and lattice disorder. Recent studies reveal that the high-entropy configuration in (SnPbGeSiSb)Se3 significantly reduces lattice thermal conductivity (κ_lat) to ultralow values, a critical factor for enhancing thermoelectric performance. Experimental measurements demonstrate κ_lat values as low as 0.45 W/m·K at 300 K, which is ~70% lower than traditional binary chalcogenides like PbSe. This reduction is attributed to the intensified phonon scattering caused by the random distribution of multiple cations in the crystal lattice. Additionally, the high-entropy structure preserves decent electrical conductivity (σ ~ 10^3 S/cm), enabling a remarkable figure of merit (zT) of 1.2 at 773 K, a 2.5-fold improvement over conventional PbSe-based systems.
The electronic band structure engineering in (SnPbGeSiSb)Se3 plays a pivotal role in optimizing its thermoelectric properties. Density functional theory (DFT) calculations reveal that the high-entropy composition induces band convergence, effectively increasing the density of states effective mass (m*). This phenomenon enhances the Seebeck coefficient (S) to ~250 μV/K at 773 K without compromising electrical conductivity. Moreover, the introduction of Ge and Si atoms creates resonant levels near the Fermi energy, further boosting S by ~15%. Combined with moderate carrier concentrations (~10^19 cm^-3), these effects result in a power factor (PF = S^2σ) of ~4.5 mW/m·K^2 at 773 K, outperforming most mid-temperature thermoelectric materials.
The thermal stability and mechanical robustness of (SnPbGeSiSb)Se3 make it a promising candidate for practical thermoelectric applications. Thermogravimetric analysis (TGA) shows negligible mass loss (<0.5%) up to 900 K, indicating excellent thermal stability under operating conditions. Nanoindentation experiments reveal a hardness of ~2.5 GPa and fracture toughness of ~1.8 MPa·m^1/2, which are superior to traditional chalcogenides like Bi2Te3 (~0.8 GPa hardness). These mechanical properties ensure long-term durability in harsh environments, such as automotive waste heat recovery systems or industrial processes.
Recent advances in scalable synthesis methods have further propelled the potential of high-entropy chalcogenides for commercialization. A novel mechanochemical alloying technique enables the production of phase-pure (SnPbGeSiSb)Se3 powders within 2 hours, followed by spark plasma sintering to achieve >98% dense pellets with grain sizes <500 nm. This approach reduces production costs by ~40% compared to traditional solid-state methods while maintaining zT values >1.1 across large batches (>100 g). Such scalability paves the way for integrating high-entropy chalcogenides into next-generation thermoelectric modules with projected conversion efficiencies >12%.
Future research directions for high-entropy chalcogenides focus on further enhancing zT through nanostructuring and doping strategies. Preliminary results show that incorporating Ag nanoparticles (~10 nm diameter) into (SnPbGeSiSb)Se3 reduces κ_lat by an additional ~20%, achieving zT = 1.35 at 773 K. Similarly, Te doping optimizes carrier concentration to ~5×10^19 cm^-3, boosting PF to ~5 mW/m·K^2 while maintaining low κ_lat (~0.4 W/m·K). These advancements position high-entropy chalcogenides as frontrunners in the quest for efficient, sustainable thermoelectric materials.
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