High-entropy silicides (HESs) have emerged as a groundbreaking class of materials for thermoelectric applications due to their unique compositional complexity and exceptional thermal stability. The (MoNbTaTiV)Si2 system, in particular, has demonstrated remarkable potential owing to its high configurational entropy and lattice distortion, which significantly reduce thermal conductivity while maintaining electrical conductivity. Recent studies have revealed that the lattice thermal conductivity of (MoNbTaTiV)Si2 can be as low as 1.8 W/m·K at 300 K, a 40% reduction compared to traditional binary silicides like MoSi2. This reduction is attributed to the phonon scattering caused by the atomic size mismatch and chemical disorder inherent in high-entropy systems. Additionally, the material exhibits a Seebeck coefficient of 220 µV/K at 800 K, making it a strong candidate for high-temperature thermoelectric applications.
The electronic structure of (MoNbTaTiV)Si2 has been meticulously engineered to optimize its thermoelectric performance. Density functional theory (DFT) calculations combined with experimental validation have shown that the multi-principal element nature of this HES creates a flat and dense electronic density of states near the Fermi level, enhancing the Seebeck coefficient without compromising electrical conductivity. Recent breakthroughs include achieving a power factor of 3.2 mW/m·K² at 900 K through precise doping strategies, such as partial substitution of Si with Ge or Al. This represents a 25% improvement over previous HES systems. Furthermore, the material’s carrier mobility has been measured at 15 cm²/V·s, which is exceptionally high for silicides, ensuring efficient charge transport even at elevated temperatures.
The mechanical robustness and thermal stability of (MoNbTaTiV)Si2 make it particularly suitable for harsh operating environments often encountered in thermoelectric devices. Nanoindentation studies have revealed a hardness value of 12 GPa and a fracture toughness of 4 MPa·m¹/², which are significantly higher than those of conventional thermoelectric materials like Bi2Te3. Thermal cycling tests conducted over 1,000 cycles between 300 K and 1,000 K showed no phase decomposition or microstructural degradation, highlighting its exceptional durability. These properties are critical for long-term device reliability in applications such as waste heat recovery in industrial processes or space exploration.
Recent advancements in synthesis techniques have further enhanced the performance of (MoNbTaTiV)Si2. Spark plasma sintering (SPS) has been employed to achieve near-theoretical density (>98%) while minimizing grain growth and preserving nanostructural features that enhance phonon scattering. This has resulted in a record-high ZT value of 0.85 at 1,000 K, surpassing most state-of-the-art high-entropy materials by over 30%. Additionally, scalable fabrication methods such as powder metallurgy and additive manufacturing are being explored to enable cost-effective production for industrial applications.
The integration of (MoNbTaTiV)Si2 into prototype thermoelectric devices has demonstrated its practical viability. A recent study reported an energy conversion efficiency of 12% under a temperature gradient of 500 K using segmented legs composed of this material paired with p-type Bi0.5Sb1.5Te3. This efficiency is comparable to commercial modules but achieved at significantly higher operating temperatures (>800 K). Furthermore, the material’s compatibility with standard metallization techniques ensures seamless integration into existing device architectures, paving the way for rapid commercialization.
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