Slowing down the heat in thermoelectrics

Heat transport has various applications in solid materials.In particular,the thermoelectric technology provides an alternative approach to traditional methods for waste heat recovery and solid-state refrigeration by enabling direct and reversible conversion between heat and electricity.For enhancing the thermoelectric performance of the materials,attempts must be made to slow down the heat transport by minimizing their thermal conductivity(κ).In this study,a continuously developing heat transport model is reviewed first.Theoretical models for predicting the lattice thermal conductivity(κlat)of materials are summarized,which are significant for the rapid screening of thermoelectric materials with lowκlat.Moreover,typical strategies,including the introduction of extrinsic phonon scattering centers with multidimensions and internal physical mechanisms of materials with intrinsically lowκlat,for slowing down the heat transport are outlined.Extrinsic defect centers with multidimensions substantially scatter various-frequency phonons;the intrinsically lowκlat in materials with various crystal structures can be attributed to the strong anharmonicity resulting from weak chemical bonding,resonant bonding,low-lying optical modes,liquid-like sublattices,off-center atoms,and complex crystal structures.This review provides an overall understanding of heat transport in thermoelectric materials and proposes effective approaches for slowing down the heat transport to depressκlat for the enhancement of thermoelectric performance.