Bengaluru: In a significant scientific breakthrough, researchers at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, have developed a cutting-edge material capable of converting waste heat into energy with unprecedented efficiency. The team, led by Professor Kanishka Biswas and his Ph.D. student Vaishali Taneja, synthesised a novel thermoelectric material by introducing twisted layers in ferecrystals, a unique class of misfit layered compounds.
The material, based on tin selenide (SnSe), exhibits a thermoelectric figure of merit of 2.3, the highest reported for n-type materials. This achievement has the potential to revolutionise thermoelectric energy conversion by capturing waste heat from industrial processes, such as those in steel plants, refineries, and vehicle exhaust systems, and converting it into usable electricity.
A Breakthrough in Thermoelectric Materials
"With about 65 per cent of all utilised energy being lost as heat in nature, thermoelectric materials offer a sustainable solution by converting waste heat into electricity without emitting harmful gases like CO2," Prof. Kanishka Biswas told ETV Bharat. “Our new n-type thermoelectric material selectively blocks heat while allowing the flow of charges, thanks to the innovative twisted layered ferecrystal nanostructures.”
The researchers achieved this breakthrough by stabilising SnSe-TaSe2 ferecrystals within a SnSe matrix through halide doping. These nanostructures act as powerful heat blockers, significantly enhancing the material's thermoelectric performance.
How Ferecrystals Work
Ferecrystals are a subclass of misfit layered compounds (MLCs), which are 2D superlattices made of alternating layers of different structures. The unique misalignment and twisting of these layers hamper heat transport while preserving electrical conductivity.
The research highlights that imbibing ferecrystals as nanostructures in a solid-state matrix presents significant challenges. However, achieving this has unlocked new possibilities in thermoelectric technology, paving the way for sustainable energy solutions.
Advanced Analytical Techniques
To confirm the successful synthesis of the intergrowth nanostructures, the team collaborated with Prof. N. Ravishankar from the Indian Institute of Science (IISc), Bengaluru. Using advanced microscopy techniques such as high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), the researchers observed the precise arrangement of TaSe2 layers within the SnSe matrix.
These analyses revealed the rotational disorder in the ferecrystals, with SnSe and TaSe2 sublattices twisted around the stacking direction (c-axis). This structural innovation is key to the material’s ability to block heat transport effectively.
"This breakthrough could lead to substantial advancements in energy efficiency and reduce dependence on traditional fossil fuels," added Prof. Biswas.
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