Evidence for hard and soft substructures in thermoelectric SnSe

Srinivasa Rao Popuri (1) , Michaël Pollet (2) , Rodolphe Decourt (2) , Mihai S. Viciu (3) , Jan-Willem G. Bos (1)

1 Institute of Chemical Sciences and Centre for Advanced Energy Storage and Recovery
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
3 Departement Chemie und Angewandte Biowissenschaften

SnSe is a topical thermoelectric material with a low thermal conductivity which is linked to its unique crystal structure. We use low-temperature heat capacity measurements to demonstrate the presence of two characteristic vibrational energy scales in SnSe with Debye temperatures θD1 = 345(9) K and θD2 = 154(2) K. These hard and soft substructures are quantitatively linked to the strong and weak Sn-Se bonds in the crystal structure. The heat capacity model predicts the temperature evolution of the unit cell volume, confirming that this two-substructure model captures the basic thermal properties. Comparison with phonon calculations reveals that the soft substructure is associated with the low energy phonon modes that are responsible for the thermal transport. This suggests that searching for materials containing highly divergent bond distances should be a fruitful route for discovering low thermal conductivity materials.

Mots clés: Chemical bonds; Heat capacity; Phonons; Thermal conductivity; Crystal structure

Domaines: Matériaux

Srinivasa Rao Popuri, Michaël Pollet, Rodolphe Decourt, Mihai S. Viciu, Jan-Willem G. Bos. Evidence for hard and soft substructures in thermoelectric SnSe . Applied Physics Letters, 2017, 110 (25), 253903 (4 p.). ⟨10.1063/1.4986512⟩. ⟨hal-01569393⟩