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B-Site Columnar-Ordered Halide Double Perovskites: Breaking Octahedra Motions Induces Strong Lattice Anharmonicity and Thermal Anisotropy by Qi Wang; Zezhu Zeng; Peng Zhao; Chen Chen; Niuchang Ouyang; Jun Mao; Yue Chen is a Materials Science article available to read on EtoBox.

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Double perovskites have attracted much interest in thermoelectric energy conversion for their ultralow thermal conductivity. Here, we report first-principles-based machine learning calculations of recently synthesized B-site columnarordered halide double perovskites Cs 2 AgB(II)X 5 (B(II): Pd or Pt; X: Cl or Br) on thermal conductivities. Unlike other double perovskites, the B(II) cation in Cs 2 AgB(II)X 5 forms a planar square with four halide anions, which breaks regular [AgX 6 ] octahedra motions and induces strong lattice anharmonicity and thermal anisotropy. We find that thermal expansion and phonon renormalization are vital to determine the harmonic and anharmonic phonon properties of these perovskites. Furthermore, contributions from both particlelike and wavelike phonons are comprised to correctly predict the ultralow thermal conductivity as revealed by experimental measurements, and at room temperature, the thermal conductivity of Cs 2 AgPdBr 5 along the x-direction is as low as 0.16 W/m K, which is among the lowest thermal conductivities of all-inorganic perovskites. Our study demonstrates the strong lattice anharmonicity caused by unusual atom vibrations that are disting

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Author

Qi Wang; Zezhu Zeng; Peng Zhao; Chen Chen; Niuchang Ouyang; Jun Mao; Yue Chen

Publisher

American Chemical Society (ACS)

Published

2023

Language

EN

Field

Materials Science (Physical Sciences)