“Twisting Layers” in Solid State: A Breakthrough in Conversion of Waste Heat to Electricity
Researchers have developed a new material capable of highly efficient waste heat-to-energy conversion by introducing twisted layers in ferecrystals. These are a unique class of misfit-layered compounds. This material, have an exceptionally high thermoelectric figure of merit(a measure of the thermoelectric performance of a material) exceeding two. Thereby, it acts as a powerful heat blocker and holds significant potential for thermoelectric energy conversion. This process captures waste heat from various sources, transforming it into electricity. Some examples are of such sources of waste heat are:
Industrial operations in chemical and thermal plants,
Steel manufacturing,
Petroleum refineries, and
Vehicle exhaust
Exploring 2D Superlattice Materials and Misfit Layered Compounds
Two-dimensional (2D) superlattice materials, composed of alternating layers of two or more different structures, are engineered at the atomic level. Each layer is typically only a few atoms thick. The periodic stacking of distinct 2D materials produces a new material with unique electronic properties absent in the individual layers.
Misfit Layered Compounds (MLCs) are a fascinating example of 2D natural superlattice materials. These compounds consist of two or more periodically stacked independent layers. The differences in the repeating patterns of these layers along one direction causes misalignment. Such a misalignment gives MLCs their distinctive structure and properties.
This misalignment creates a ‘misfit’ between the layers. In a unique class of MLCs known as ferecrystals, the rotational disorder (twisting between layers) significantly disrupts heat transport. This ends up effectively blocking heat waves in the material. This property makes ferecrystals particularly valuable for thermoelectric energy conversion, enabling the transformation of waste heat into electricity.
However, incorporating ferecrystals as nanostructures within a solid-state matrix remains a significant challenge in synthetic chemistry and materials science. Successfully overcoming this challenge could drive substantial advancements in thermoelectric technology and expand the possibilities of current material synthesis techniques.
Advancing Thermoelectric Materials: Breakthrough in SnSe-TaSe₂ Ferecrystals for Energy Efficiency
In a recent study, Professor Kanishka Biswas, along with his Ph.D. student Ms. Vaishali Taneja from the New Chemistry Unit at Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru—an autonomous institution under the Department of Science & Technology, Government of India—and other team members, synthesized ferecrystalline intergrowths as nanoscale regions within bulk SnSe combined with n-type halide doping. This effort led to the stabilization of SnSe-TaSe2 ferecrystals as nanostructures within a solid-state SnSe matrix. The structures function as highly effective heat blockers. The thermoelectric figure of merit achieved in this work is 2.3.
Published in the Journal of the American Chemical Society, this study represents a significant step toward achieving high-performance n-type SnSe polycrystals. To confirm the formation of the intended intergrowth nanostructures, the team collaborated with Professor N. Ravishankar from IISc, Bengaluru, using high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) analysis. These techniques revealed the presence of TaSe2layers after every seven bilayers of SnSe. The researchers also identified extensive rotational disorder in the ferecrystals. In these, SnSe and TaSe2sublattices are twisted around the stacking direction (c-axis) and translated perpendicularly to it. These findings have the potential to significantly enhance energy efficiency and contribute to greater sustainability.
A schematic and HAADF-STEM image illustrating the ferecrystalline intergrowths. These result in ultrahigh thermoelectric performance in Ta and Br co-doped SnSe.
Vaishali Taneja (left) and Kanishka Biswas (right), JNCASR, Bangalore
References
http://www.pib.gov.in/Pressreleaseshare.aspx?PRID=2082370
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