Crystalline solids with low lattice thermal conductivity (κL) provide an exciting podium to develop a fundamental understanding of the correlation between chemical bonding and lattice dynamics along with their influence on the thermal transport. Layered intergrowth compounds in the homologous (SnTe)m(M2Te3)n (M = Sb/Bi) family are interesting in this aspect because they represent the natural "van der Waals heterostructures". However, most of the layered compounds from the above series exhibit incongruent melting point, which make synthesis of the phase pure compounds challenging through traditional high-temperature solid-state route. Herein, we show the stabilization of these layered intergrowth phases in the form of nanostructure, which is intriguing in terms of fundamental solid state inorganic chemistry and nanoscience. HRTEM and HAADF-STEM reveal the stacking sequence and van der Waals heterostructured nature. Due to formation of stable nanodomains of the Sb-rich layered intergrowth SnmSb2nTe3n+m in SnTe via matrix encapsulation, κL near to the theoretical minimum limit, κmin has been realized in well known Pb- free thermoelectric material, Sb alloyed SnTe. This can be attributed to efficient phonon scattering through both (a) the interface between matrix and nanodomain and (b) the interfaces between the layers of heterostructures. Few-layer nanosheets of layered intergrowth compounds, SnmBi2nTe3n+m synthesized via simple low temperature solution based synthesis, exhibit ultra-low κL (~0.4 Wm-1K-1) due to significant phonon scattering by heterostructure interfaces and layer staking faults. Our finding reveals a unique solution towards the synthesis of layered intergrowth compound that allows their scalable production along with controlled manipulation of physical properties.

Layered intergrowth compounds for ultralow thermal conductivity

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.