Alignment of edge dislocations – the reason lying behind composition inhomogeneity induced low thermal conductivity

Compositional inhomogeneity in a material can result in low thermal conductivity, benefiting applications such as thermoelectric energy conversion, energy gas storage, and thermal barrier coating. However, current understanding remains limited to effective thermal conductivity models, which largely overlook detailed structural features of the material. Here, taking Bi_0.4Sb_1.6Te₃ compound as a proof-of-concept material, we reveal that the true reason for low thermal conductivity determined by compositional inhomogeneity originates from randomly aligned edge dislocations. The random alignment of edge dislocations is consistent with the alignment of composition distribution. This is because these edge dislocations are primarily gathered at composition gradient domains between domains with different compositions, having preferential orientation along the composition gradient direction. This work offers a structural perspective on the mechanism underlying reduced thermal conductivity due to compositional inhomogeneity, providing valuable insights for designing materials with tailored thermal properties.