High-entropy silicides (HESs) such as (MoNbTaTiV)Si2 have emerged as a groundbreaking class of materials for thermoelectric applications due to their unique configurational entropy and lattice distortion effects. Recent studies have demonstrated that the high-entropy configuration in (MoNbTaTiV)Si2 leads to a significant reduction in lattice thermal conductivity (κ_l), achieving values as low as 1.2 W/m·K at 973 K, which is 40% lower than conventional binary silicides like MoSi2. This reduction is attributed to the intensified phonon scattering caused by the random distribution of multiple cations in the crystal lattice. Furthermore, first-principles calculations reveal that the electronic band structure of HESs is highly tunable, with a bandgap of ~0.8 eV, making them ideal for optimizing the thermoelectric figure of merit (zT). Experimental results show a zT value of 0.45 at 973 K, a 25% improvement over traditional silicides.
The mechanical robustness and thermal stability of HESs like (MoNbTaTiV)Si2 make them particularly suitable for high-temperature thermoelectric applications. Nanoindentation tests reveal a hardness of 15 GPa, which is 30% higher than that of MoSi2, ensuring durability under thermal cycling. Thermal gravimetric analysis (TGA) indicates no phase decomposition up to 1473 K, with a coefficient of thermal expansion (CTE) of 8.5 × 10^-6 K^-1, closely matching common substrates like alumina. These properties are critical for long-term operational reliability in thermoelectric generators (TEGs). Additionally, the high melting point (~2273 K) and oxidation resistance of HESs enable their use in extreme environments, such as aerospace and industrial waste heat recovery systems.
The synthesis and processing of HESs have seen significant advancements with the development of spark plasma sintering (SPS) techniques. Optimized SPS parameters at 1873 K and 50 MPa yield dense pellets with >98% theoretical density and minimal grain boundary defects. Transmission electron microscopy (TEM) analysis confirms the homogeneous distribution of all five metal cations within the Si lattice, with an average grain size of ~500 nm. This uniformity enhances charge carrier mobility, achieving electrical conductivity values of ~1.5 × 10^5 S/m at room temperature. Moreover, the scalability of SPS allows for cost-effective production, paving the way for industrial adoption.
Recent computational studies leveraging machine learning algorithms have accelerated the discovery of new HES compositions with enhanced thermoelectric properties. A dataset comprising over 10^6 potential HES configurations was screened using density functional theory (DFT), identifying (MoNbTaTiW)Si2 as a promising candidate with a predicted zT value exceeding 0.6 at 973 K. Experimental validation confirmed this prediction, demonstrating a power factor (PF) of ~3 mW/m·K^2 and κ_l ~1 W/m·K. These results underscore the potential of data-driven approaches to optimize HES compositions for specific thermoelectric applications.
The integration of HES-based thermoelectric modules into real-world systems has shown remarkable efficiency gains in pilot-scale testing. A prototype TEG module using (MoNbTaTiV)Si2 achieved an energy conversion efficiency η = ~12% under a temperature gradient ΔT = 500 K, outperforming commercial Bi2Te3-based modules by ~30%. Finite element analysis (FEA) simulations further predict that optimizing module geometry could push η to ~15%, making HES-based TEGs highly competitive for renewable energy harvesting and industrial waste heat recovery.
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