TlCu5Se3– Unusual Wave-like Thermal Transport
Why in News?
Researchers at Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru (autonomous under Department of Science & Technology) reported an unusual wave-like thermal transport regime in a copper chalcogenide crystal: thallium copper selenide (TlCu₅Se₃).
Scientific Breakthrough
- Challenging Physics Norms: In conventional crystalline solids, heat travels as particle-like packets of energy called phonons. In TlCu₅Se₃, heat transport transitions to a wave-like coherence where phonons effectively tunnel between vibrational states.
- The "Phonon Glass, Electron Crystal" Ideal: The material conducts electricity cleanly like a crystal, but blocks heat as effectively as glass.
- Ultralow Conductivity: It demonstrates an intrinsically low lattice thermal conductivity (0.3–0.2 W m⁻¹ K⁻¹ across temperatures ranging from 294–673 K).
Why TlCu₅Se₃ is Distinctive? (The Mechanism)
- Complex "Knot-like" Architecture: TlCu₅Se₃ crystallises into a complex, three-dimensional cloverleaf knot-like framework featuring open channels.
- Confined Local Disorder: Many conventional materials achieve low thermal conductivity via highly mobile ions that move freely like a liquid (superionic conductors), but this triggers structural breakdown over time. In this compound, the copper (Cu) atoms are locked in place but undergo intense localized dynamic disorder (they "rattle" but cannot escape).
- Extreme Anharmonicity: This confined atomic rattling causes highly asymmetric atomic vibrations (anharmonicty), disrupting regular heat travel and causing the wave-like phonon transport.
Record-Breaking Performance
- High Figure of Merit (zT): The material yields a thermoelectric figure of merit (zT) of 1.7 at 673 K.
- Top Tier Ranking: A 1.7 zT score places TlCu₅Se₃ among the highest-performing pristine ternary chalcogenide materials ever reported for thermoelectric energy transformation.
Who Conducted the Research?
- Experimental Team: Led by Prof. Kanishka Biswas along with Ph.D. students Ms. Sayantoni Choudhury and Dr. Animesh Bhui from the New Chemistry Unit (NCU) at JNCASR.
- Theoretical Team: Advanced first-principles calculations and molecular simulations were spearheaded by Prof. Umesh V. Waghmare and Dr. Prasad V. Matukumilli from the Theoretical Sciences Unit (TSU) at JNCASR.
Practical Applications
By converting temperature differences directly into electricity (the Seebeck effect), this material could be vital for harvesting waste heat:
By converting temperature differences directly into electricity (the Seebeck effect), this material could be vital for harvesting waste heat:
- Industrial Waste Heat Recovery: Capturing lost thermal energy from high-intensity environments like steel plants, cement factories, and power plants.
- Automotives & Electronics: Boosting fuel/energy efficiency in automobiles and managing internal temperatures in dense data centres.
- Advanced Tech: Thermal management in lithium batteries, structural thermal barrier coatings, and building decoherence-free quantum technologies.
