Phonon Symphony of Stacked Multilayers and Weak Bonds Lowers Lattice Thermal Conductivity. Issue 30 (19th June 2022) - Ma, Ni
Abstract: Controlling lattice vibrations to obtain intrinsic low thermal conductivity play a critical role in thermal management of electronic and photonic devices, energy converters, and thermal insulation, which necessitates exploring new compounds and a thorough understanding of their chemical structure, bonding, and lattice dynamics. Herein, a new chalcogenide, Ga6 Cr5 Se16, shows intrinsic low lattice thermal conductivity κlat, which crystallizes in the monoclinic phase ( C 2/ m ) with the stacked inverse GaSe4 layers ( g '), close‐packed Cr 3+ Se6 layers ( c ), GaSe4 layers ( g ) and loosely‐stacked Cr 2+ Se6 layers ( c ') along the c ‐axis. In this structure, a wide variety of chemical bonding is arranged in each layer, such as covalent Ga–Se, covalent Cr 3+ –Se, and weaker Cr 2+ –Se bonding, which endow it with a large phonon symphony by strong coupling of soft acoustic and low‐lying optical phonons. As a result, Ga6 Cr5 Se16 realizes an intrinsic low κlat of 0.79 W m − 1 K − 1 at 323 K, which is almost four times, or twice lower than that of Cr3 Se4 (2.95 W m − 1 K − 1 ), or Cr2 Se3 (1.56 W m − 1 K − 1 ), Ga2 Se3 (1.36 W m − 1 K − 1 ) at 323 K, respectively. These insights will offer comprehensive understanding of the phonon propagation in complex layered chalcogenides, and also shed useful light on future design of low‐κlat solids. Abstract : A new chalcogenide, Ga6 Cr5 Se16, shows intrinsic low lattice thermal conductivity (0.79 W m −1 K −1 ) at 323 K, which is almost four times lower than that of binary Cr3 Se4 ), or twice lower than that of Cr2 Se3 and Ga2 Se3 . This work provides a comprehensive understanding of the phonon propagation in layered chalcogenides, elucidates a direction for the rational design of multilayer stacking in solids with low κlat .