Controlled\nPhonon Transport via Chemical Bond Stretching\nand Defect Engineering: The Case Study of Filled β‑Mn-Type\nPhases

Controlling the elastic properties of the material could\nbecome\na powerful tool for tuning the thermal transport in solids. Nevertheless,\nthe impact of the crystal structure, chemical bonding, and elastic\nproperties on the lattice thermal conductivity remains to be elucidated.\nThis is a pivotal issue for the advancement of thermoelectric (TE)\nmaterials. In this context, the influence of cation substitution in\ntetrahedral voids on the structural, thermal, and TE properties of\nα- and β-Pb<sub><i>y</i></sub>Ga<sub>6–<i>x</i></sub>In<sub><i>x</i></sub>Te<sub>10</sub>filled\nβ-Mn-type phasesis reported here. The investigated materials\nshow semiconducting behavior and a change from p- to n-type conductivity,\ndepending on the chemical composition and temperature. Our findings\nindicate that the electronic transport in β-Mn-type phases is\nlargely influenced by the substantial distortion of the Te framework,\nwhich causes the low weighted mobility and strong scattering of charge\ncarriers. The presence of a significant anharmonicity of lattice vibrations\nresults in the ultralow lattice thermal conductivity of Pb<sub><i>y</i></sub>Ga<sub>6–<i>x</i></sub>In<sub><i>x</i></sub>Te<sub>10</sub> materials. With increasing <i>x</i>, κ<sub>L</sub> decreases from 0.59 to an extremely\nlow value of 0.36 W m<sup>–1</sup> K<sup>–1</sup> at\n298 K due to the decrease of bonding energy, intensification of anharmonic\nthermal vibrations of atoms, and formation of point defects. This\nwork demonstrates the efficacy of utilizing the crystal structure\nand elastic properties to regulate phonon transport in functional\nmaterials.