SESSION 1D: Symposium: Materials of Today and Tomorrow

A K Ganguli, IIT Delhi

Low thermal conductive chalcogenides for high performance thermoelectric energy conversion View Presentation

One of the fundamental challenges in developing high-performance thermoelectric materials has been to achieve low lattice thermal conductivity (κL). Intrinsic low thermal conductivity is of practical interest due to its robustness against grain size, temperature range and other structural variations. The exploration of new materials with intrinsically low κL along with a microscopic understanding of the underlying correlations among bonding, lattice dynamics and phonon transport is fundamentally important towards designing promising thermoelectric materials. Zintl compounds, TlInTe2 , exhibit ultralow κL due to low energy ratting modes (optical modes) of weakly bound Tl+. These low energy optic phonon modes are strongly anharmonic, which scatter the heat-carrying acoustic phonons through phonon–phonon interactions, thereby decrease the thermal conductivity. Soft phonon modes and optical–acoustic phonon coupling cause an ultralow κL in the room-temperature hexagonal phase of AgCuTe, while the dynamic disorder of Ag/Cu cations leads to reduced phonon frequencies and mean free paths in the high-temperature rocksalt phase. A high zT of 1.6 is achieved in the p-type AgCuTe at ~670 K. The speakers’s group has recently shown that the localized vibrations of Bi bilayer lead to ultralow lattice thermal conductivity and high thermoelectric performance in weak topological insulator n-type BiSe near room temperature.