Unraveling the structural details and thermoelectric transports of 2D-3D hetero-structure composites

With in-depth research on the thermoelectric properties of the single-phase traditional three-dimensional (3D) and emerging two-dimensional (2D) materials, there is a deficit in the study of the 2D-3D hetero-structure phases, whose structural details and transport features still require a clear understanding. In this work, taking 2D-SnSe and 3D-PbSe as research objects, we prepared mixture-phase composites with the coexistence of 2D and 3D phases and studied the relationship between the thermoelectric transports and phase structures. By con-ducting the powder X-ray diffraction measurements and Rietveld refinements, we obtained the dynamic 2D-3D hetero-structure compositions of weight percentages with heating-cooling cycles. Subsequently, we estimated the lattice thermal conductivity from the experimental measurements and theoretical calculations as functions of 2D-3D compositions. We discovered that the lattice thermal conductivity reduction became more obvious in the samples with small amounts of hetero-structure phases, benefiting from the extra scattering of phonons by the higher density of hetero-structure interfaces. Moreover, we observed the 2D-3D hetero-structures at the micro-scopic scale by HADDF-STEM, experimentally confirming the presence of low symmetrical-PbSe and high symmetrical-SnSe phases. This study gave a perspective and investigation method to unravel both the structural details and transport properties of 2D-3D hetero-structure composites, which might provide new strategies for optimizing thermoelectric performance by depressing the thermal transports in hetero-structure materials.

Automated summary

With in-depth research on the thermoelectric properties of 2D and 3D materials, the study explores the relationship between thermoelectric transport and phase structures of 2D-3D heterostructures. Through experimental measurements and theoretical calculations, it is discovered that the reduction in lattice thermal conductivity is more significant in samples with small amounts of heterostructure phases. The presence of low symmetrical-PbSe and high symmetrical-SnSe phases in the heterostructures is experimentally confirmed at the microscopic scale. This study provides a perspective and investigation method to unravel the structural details and transport properties of 2D-3D heterostructure composites.