Journal of Materials Science and Nanomaterials
Open Access

Thermoelectric Materials; Nanostructuring; Silicon-Germanium Alloys; Bismuth Telluride; Perovskites; Skutterudites; Half-Heusler Alloys; Organic Thermoelectrics; Two-Dimensional Materials; Tin Selenide

Introduction

The field of thermoelectric materials is undergoing rapid advancement, driven by the growing need for sustainable energy solutions and efficient waste heat recovery systems. Nanostructuring has emerged as a pivotal strategy for optimizing the thermoelectric performance of various material classes. One significant area of research involves nanostructured silicon-germanium alloys, where controlling grain boundaries and nanodomain structures demonstrably enhances thermoelectric properties such as the Seebeck coefficient and electrical conductivity while simultaneously reducing thermal conductivity, thereby improving device efficiency [1].

Bismuth telluride, a long-standing material for thermoelectric cooling, is also being explored for enhanced mid-temperature applications. Strategies like doping with rare-earth elements have shown promise in significantly reducing lattice thermal conductivity, leading to a higher figure of merit (ZT) and offering a promising avenue for more efficient thermoelectric generators operating at intermediate temperatures [2].

Perovskite materials, particularly lead-free halide perovskites, are attracting considerable attention for thermoelectric applications, especially in waste heat recovery. Their tunable band gaps and potential for structural stability make them attractive candidates for sustainable and efficient thermoelectric devices, exhibiting a promising combination of a high Seebeck coefficient [3].

Skutterudites, specifically CoSb3-based compounds, are another class of materials being engineered for improved thermoelectric performance. The introduction of nanoinclusions into skutterudites effectively scatters phonons, leading to a substantial reduction in thermal conductivity without significantly compromising electrical transport properties, a key approach to achieving higher ZT values [4].

Magnesium-based Zintl phases are being investigated as potential thermoelectric materials for mid-to-high temperature applications. Research into varying stoichiometry and introducing alloying elements has revealed promising results, including reduced thermal conductivity and an increased Seebeck coefficient, indicating their viability for these demanding applications [5].

Organic thermoelectric materials, such as advanced conjugated polymers, offer advantages like flexibility and low-cost processing. While often limited by low ZT values, novel functionalization strategies focusing on enhancing charge carrier mobility and reducing thermal conductivity are making these materials more competitive for flexible electronic applications [6].

Polycrystalline indium selenide is another material system where grain boundary engineering plays a crucial role in optimizing thermoelectric properties. Controlling grain size and texture influences phonon scattering and charge transport, with optimized grain structures demonstrably reducing lattice thermal conductivity and improving the thermoelectric figure of merit [7].

Half-Heusler alloys remain a critical area of research for high-temperature thermoelectric applications. Alloying and nanostructuring are key techniques used to optimize their thermoelectric properties. Significant improvements in ZT values have been reported due to reduced thermal conductivity and enhanced power factor, underscoring their potential for efficient power generation [8].

Two-dimensional (2D) materials, including graphene and transition metal dichalcogenides (TMDCs), are being explored for advanced thermoelectric energy harvesting. Their unique electronic and thermal transport properties, combined with strategies like functionalization and heterostructure formation, offer pathways for developing highly efficient and flexible thermoelectric devices with enhanced figures of merit [9].

Tin selenide (SnSe), a promising p-type material, is being investigated in nanostructured form for enhanced thermoelectric generator (TEG) efficiency. Controlling its nanostructure and crystal orientation has been shown to significantly enhance the Seebeck coefficient and reduce thermal conductivity, leading to improved ZT values essential for practical TEG applications [10].

Description

Novel n-type thermoelectric materials based on nanostructured silicon-germanium alloys are being developed, with research highlighting how precise control over grain boundaries and nanodomain structures is critical. This engineering at the nanoscale leads to significant enhancements in the Seebeck coefficient and electrical conductivity, while simultaneously suppressing thermal conductivity, establishing a clear pathway for improving the overall efficiency of thermoelectric devices [1].

The performance of bismuth telluride, a staple in thermoelectric cooling, is being actively enhanced for mid-temperature ranges. This study demonstrates that doping with rare-earth elements is an effective strategy to optimize its thermoelectric properties. Such doping significantly reduces lattice thermal conductivity, resulting in a higher figure of merit (ZT), which is crucial for developing more efficient thermoelectric generators operating at intermediate temperatures [2].

Perovskite materials, especially a new class of lead-free halide perovskites, are being investigated for their immense potential in thermoelectric applications, particularly for waste heat recovery. This research focuses on their structural stability and thermoelectric properties, with synthesized materials exhibiting a promising combination of a high Seebeck coefficient and tunable band gap, paving the way for sustainable and efficient thermoelectric energy harvesting devices [3].

The impact of nanostructuring on the thermoelectric performance of skutterudites is explored through the introduction of nanoinclusions into CoSb3-based materials. This paper details how these nanoinclusions effectively scatter phonons, leading to a substantial reduction in thermal conductivity. Critically, this reduction in thermal conductivity is achieved without significantly compromising the material's electrical transport properties, a crucial factor for achieving higher ZT values [4].

Magnesium-based Zintl phases are being characterized as potential thermoelectric materials, with research focusing on the synthesis and optimization of their properties. Investigations into varying stoichiometry and introducing alloying elements are revealing effects on the electronic structure and lattice dynamics. Promising results include a reduction in thermal conductivity and an increase in the Seebeck coefficient, demonstrating their viability for mid-to-high temperature thermoelectric applications [5].

Organic thermoelectric materials, specifically advanced conjugated polymers functionalized with specific side chains, are being developed to overcome limitations in flexibility and processing costs. This work investigates strategies to improve charge carrier mobility and reduce thermal conductivity. The study reports a significant enhancement in the thermoelectric power factor, making these materials more competitive for the growing field of flexible electronics [6].

The effect of grain boundary engineering on the thermoelectric properties of polycrystalline indium selenide is a key focus of this research. The paper investigates how controlled grain size and texture influence phonon scattering and charge transport mechanisms. The findings reveal that optimized grain structures can significantly reduce lattice thermal conductivity, leading to a marked improvement in the thermoelectric figure of merit for this material [7].

Half-Heusler alloys continue to be a critical area of research for high-temperature thermoelectric applications, with this study focusing on optimizing Ni-based half-Heuslers through alloying and nanostructuring. Significant improvements in ZT values are reported, primarily attributed to reduced thermal conductivity and an enhanced power factor. These results further underscore the considerable potential of these alloys for efficient thermoelectric power generation [8].

Two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDCs), are being explored for their potential in thermoelectric energy harvesting. This research highlights their unique electronic and thermal transport properties and discusses strategies for enhancing their thermoelectric figure of merit through functionalization and heterostructure formation. The findings suggest a promising pathway for developing highly efficient and flexible thermoelectric devices [9].

Nanostructured tin selenide (SnSe), a promising p-type material, is being investigated for its role in enhancing thermoelectric generator (TEG) efficiency. The research demonstrates that controlling the nanostructure and crystal orientation significantly improves the Seebeck coefficient and reduces thermal conductivity. These advancements lead to improved ZT values, making SnSe a more viable material for practical TEG applications [10].

Conclusion

This collection of research highlights advancements in thermoelectric materials, focusing on strategies to enhance energy conversion efficiency. Studies explore nanostructuring of silicon-germanium alloys and tin selenide to optimize electrical and thermal transport properties. Doping of bismuth telluride with rare-earth elements and alloying/nanostructuring of half-Heusler alloys are presented as effective methods for improving mid-to-high temperature thermoelectric performance. Research also delves into lead-free halide perovskites and organic conjugated polymers for sustainable and flexible thermoelectric applications. Furthermore, grain boundary engineering in indium selenide and nanoinclusion engineering in skutterudites are discussed as key techniques for reducing thermal conductivity and boosting the figure of merit. The potential of two-dimensional materials like graphene and TMDCs for advanced thermoelectric energy harvesting is also investigated, emphasizing the broad scope of material innovation in this field.

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