Evidence for hard and soft substructures in thermoelectric SnSe

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...

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Bibliographic Details
Published in:Applied physics letters 2017-06, Vol.110 (25)
Main Authors: Popuri, S. R., Pollet, M., Decourt, R., Viciu, M. L., Bos, J. W. G.
Format: Article
Language:English
Subjects:
Applied physics
Bonding strength
Chemical Sciences
Crystal structure
Heat conductivity
Heat transfer
Material chemistry
Specific heat
Substructures
Temperature
Thermal conductivity
Thermodynamic properties
Thermoelectric materials
Thermoelectricity
Tin selenide
Unit cell
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Summary: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.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4986512