Glassy thermal conductivity in Cs<sub>3</sub>Bi<sub>2</sub>I<sub>6</sub>Cl<sub>3</sub> single crystal.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36030224.
- Also identified by DOI 10.1038/s41467-022-32773-4 and PMC identifier 9420152.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
As the periodic atomic arrangement of a crystal is made to a disorder or glassy-amorphous system by destroying the long-range order, lattice thermal conductivity, κ<sub>L</sub>, decreases, and its fundamental characteristics changes. The realization of ultralow and unusual glass-like κ<sub>L</sub> in a crystalline material is challenging but crucial to many applications like thermoelectrics and thermal barrier coatings. Herein, we demonstrate an ultralow (~0.20 W/m·K at room temperature) and glass-like temperature dependence (2-400 K) of κ<sub>L</sub> in a single crystal of layered halide perovskite, Cs<sub>3</sub>Bi<sub>2</sub>I<sub>6</sub>Cl<sub>3</sub>. Acoustic phonons with low cut-off frequency (20 cm<sup>-1</sup>) are responsible for the low sound velocity in Cs<sub>3</sub>Bi<sub>2</sub>I<sub>6</sub>Cl<sub>3</sub> and make the structure elastically soft. While a strong anharmonicity originates from the low energy and localized rattling-like vibration of Cs atoms, synchrotron X-ray pair-distribution function evidence a local structural distortion in the Bi-halide octahedra and Cl vacancy. The hierarchical chemical bonding and soft vibrations from selective sublattice leading to low κ<sub>L</sub> is intriguing from lattice dynamical perspective as well as have potential applications.