Pseudopolymorphic Phase Engineering for Improved Thermoelectric Performance in Copper Sulfides.
basic_science · Level V
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- Record sourced from PubMed, PMID 37903494.
- Also identified by DOI 10.1002/adma.202308353.
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Abstract
Polymorphism (and its extended form - pseudopolymorphism) in solids is ubiquitous in mineralogy, crystallography, chemistry/biochemistry, materials science, and the pharmaceutical industries. Despite the difficulty of controlling (pseudo-)polymorphism, the realization of specific (pseudo-)polymorphic phases and associated boundary structures is an efficient route to enhance material performance for energy conversion and electromechanical applications. Here, this work applies the pseudopolymorphic phase (PP) concept to a thermoelectric copper sulfide, Cu<sub>2-</sub> <sub>x</sub> S (x ≤ 0.25), via CuBr<sub>2</sub> doping. A peak ZT value of 1.25 is obtained at 773 K in Cu<sub>1.8</sub> S + 3 wt% CuBr<sub>2</sub> , which is 2.3 times higher than that of a pristine Cu<sub>1.8</sub> S sample. Atomic-resolution scanning transmission electron microscopy confirms the transformation of pristine Cu<sub>1.8</sub> S low digenite into PP-engineered high digenite, as well as the formation of (semi-)coherent interfaces between different PPs, which is expected to enhance phonon scattering. The results demonstrate that PP engineering is an effective approach for achieving improved thermoelectric performance in Cu-S compounds. It is also expected to be useful in other materials.