Revealing Atomistic Ion Migration Pathways of Orientation-Dependent Long-Range Cu<sup>+</sup> Ion Migration in β-Cu<sub>2</sub>Se.
basic_science · Level V
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- Record sourced from PubMed, PMID 40029110.
- Also identified by DOI 10.1021/acs.nanolett.5c00109.
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Abstract
Understanding the long-range migration behavior of Cu<sup>+</sup> ions is essential for stabilizing β-Cu<sub>2</sub>Se-based thermoelectrics at intermediate temperatures. A pivotal remaining issue is that the correlation between long-range migration and short-range hopping of Cu<sup>+</sup> ions has not yet been established. In this study, we conduct <i>in situ</i> Cs-TEM and first-principles calculations to investigate the long-range migration of Cu<sup>+</sup> ions in β-Cu<sub>2</sub>Se. The results show Cu<sup>+</sup> ions preferentially migrate along the ⟨111⟩ directions with lower energy barriers and higher precipitation rates compared to the ⟨001⟩ directions. Such orientation-dependent long-range migration behavior is governed by the short-range hopping dynamics of Cu<sup>+</sup> ions. Along ⟨111⟩, the octahedral sites bridge the hopping of Cu<sup>+</sup> ions between tetrahedral sites, leading to a reduced energy barrier as low as 0.19 eV, which promotes the long-range migration of Cu<sup>+</sup> ions along the ⟨111⟩ direction. These insights highlight the significance of understanding lattice dynamics in regulating ion migration behavior or stabilizing ionic materials.