Glass-like thermal conduction in crystalline Mg2Sn-based high-entropy materials

Abstract

Understanding and engineering thermal transport in complex structures is essential for the development of materials with ultralow lattice thermal conductivity. In this study, we examine the unusual thermal transport behavior of Mg₂Sn-based high-entropy materials, using a combination of pair distribution function (PDF) analysis, first-principles calculations, and theoretical modeling. Our findings demonstrate that the crystalline high-entropy materials exhibit glass-like thermal transports, characterized by an exceptionally low lattice thermal conductivity that increases monotonically with increasing temperature across the entire measured range, devoid of the characteristic peaks typical of crystalline materials. This unique behavior is attributed to the large atomic displacement parameter (ADP) of Mg atoms, which causes the Einstein oscillators to significantly reduce lattice thermal conductivity, complemented by the strong scattering of phonons by the nanoscale chemical fluctuations and a dense concentration of point defects within the high-entropy structure. These insights deepen our understanding of thermal transport in complex-structured materials, such as Mg₂Sn-related compounds, and offer a foundation for designing new materials with tailored thermal conductivities for advanced thermal management and thermoelectric applications.