High Thermoelectric Performance in Non‐Toxic Earth‐Abundant Copper Sulfide

He, Yiyong; Day, Tristan; Zhang, Tiansong; Liu, Huili; Shi, Xun; Chen, Lidong; Snyder, G. Jeffrey

doi:10.1002/adma.201400515

Cited by 678 publications

(667 citation statements)

References 34 publications

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“…The electron diffraction pattern obtained from the H-i phase is purely hexagonal, with no superlattice--reflecting the absence of a structural modulation in this phase. Previous resistivity studies at various levels of nonstoichiometry in Cu 2−x S showed that the phase transition is abrupt on heating and cooling only when the Cu vacancies (x) present are less than 1% of the atomic weight (15), thus confirming the stoichiometry of our nanoparticles. Since Cu vacancies are acceptors in Cu 2 S, the hole carrier (hereafter denominated as "e + ") concentration in our p-type nanoplates n e + is less than 1%.…”

Section: Resultssupporting

confidence: 56%

Reversible structure manipulation by tuning carrier concentration in metastable Cu ₂ S

Tao

Chen

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The optimal functionalities of materials often appear at phase transitions involving simultaneous changes in the electronic structure and the symmetry of the underlying lattice. It is experimentally challenging to disentangle which of the two effects--electronic or structural--is the driving force for the phase transition and to use the mechanism to control material properties. Here we report the concurrent pumping and probing of Cu 2 S nanoplates using an electron beam to directly manipulate the transition between two phases with distinctly different crystal symmetries and charge-carrier concentrations, and show that the transition is the result of charge generation for one phase and charge depletion for the other. We demonstrate that this manipulation is fully reversible and nonthermal in nature. Our observations reveal a phase-transition pathway in materials, where electron-induced changes in the electronic structure can lead to a macroscopic reconstruction of the crystal structure. functional and quantum materials--the key properties of functional materials are often born out of strong structural and electronic interactions that are quantum mechanical in nature. Notable examples include colossal magnetoresistance manganites (1), ferroelectrics (2), and valleytronic materials (3). The targeted functions are usually accompanied by symmetry breaking, induced through changes in temperature or under other external perturbations. A prominent question is whether the symmetry reduction has an origin in the lattice (e.g., in the form of displacement of atoms, and could be described reasonably well using first-principles calculations) or the electronic degrees of freedom (charge, spin, and orbital) (4-6). It is of great interest to distinguish the roles of these factors in phase transitions.Cu 2 S provides an intriguing example for addressing the above "chicken-and-egg" question (6), which is critical to the understanding of a wide range of functional and quantum materials. It is a fast ionic conductor (7) with highly mobile Cu ions. A phase transition in the bulk material occurs near 100°C from a semiconducting (8) monoclinic symmetry low-chalcocite phase (9) [hereafter called the "L-s phase" (i.e., low, semiconducting); space group P2 1 /c] to an electrically insulating (10) hexagonal symmetry high-chalcocite phase (7, 11) [hereafter called the "H-i phase" (i.e., high, insulating); space group P6 3 /mmc]. The coinciding changes in the bulk electrical conductivity and crystal structure present a possibility for exploring the relationship between electronic and structural phase transitions. Difficulties in the synthesis of stoichiometric Cu 2 S material and the lack of detailed theoretical treatments of both the crystal and the electronic structures of Cu 2 S have hindered the understanding of the phase transition (7, 11-13). Results and DiscussionWe have recently synthesized high-quality Cu 2 S nanoplates (Materials and Methods), which are on the order of 10-nm thick and 100 nm in lateral dimension ( Fig. 1 A and B)....

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Section: Resultssupporting

confidence: 56%

Reversible structure manipulation by tuning carrier concentration in metastable Cu ₂ S

Tao

Chen

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…27 Liquid-like behavior of Cu ion in the p-type Cu 2−δ S (δ = 0-0.03) affects thermal properties. 28 With increasing temperature, the heat capacity at constant pressure C p decreased clearly at T > 400 K and fell below the Dulong-Petit value at T > 800 K, leading to the reduction in κ ∝ C p . The suppression in C p was due to the reduction in C v , the specific heat at constant volume.…”

Section: B Digenite and Chalcocite (P-type)mentioning

confidence: 99%

“…The increase in C p with T in excess of the Dulong-Petit value is in contrast with the suppression in C v (T) or C p (T) reported for superionic conductors Cu 2−δ S and Cu 2−δ Se. 28,29 Therefore, Cu ions in the colusites are not in a liquid-like state but in a localized state. Although the ZT values for the colusite are lower than that for Cu 2−δ S, higher usability of colusites for the TE applications is observed due to less migration of Cu ions.…”

Section: Colusite (P-type)mentioning

confidence: 99%

Research Update: Cu–S based synthetic minerals as efficient thermoelectric materials at medium temperatures

2016

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Synthetic minerals and related systems based on Cu–S are attractive thermoelectric (TE) materials because of their environmentally benign characters and high figures of merit at around 700 K. This overview features the current examples including kesterite, binary copper sulfides, tetrahedrite, colusite, and chalcopyrite, with emphasis on their crystal structures and TE properties. This survey highlights the superior electronic properties in the p-type materials as well as the close relationship between crystal structures and thermophysical properties. We discuss the mechanisms of high power factor and low lattice thermal conductivity, approaching higher TE performances for the Cu–S based materials.

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“…Current efforts to improve zT are focused on the optimization of power factor α 2 σ through controlled doping or electron band engineering,7, 8, 9, 10, 11 suppression in κ L by alloying or nanostructuring,1, 2, 5, 6 and development of new materials with intrinsically low κ L 12, 13, 14, 15. Heat‐carrying phonons cover a broad spectrum of frequency, and the κ L is a sum of contributions from phonons of different frequencies.…”

mentioning

confidence: 99%

Enhancing the Figure of Merit of Heavy‐Band Thermoelectric Materials Through Hierarchical Phonon Scattering

Liu

et al. 2016

Advanced Science

154

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Hierarchical scattering is suggested as an effective strategy to enhance the figure of merit zT of heavy‐band thermoelectric materials. Heavy‐band FeNbSb half‐Heusler system with intrinsically low carrier mean free path is demonstrated as a paradigm. An enhanced zT of 1.34 is obtained at 1150 K for the Fe1.05Nb0.75Ti0.25Sb compound with intentionally designed hierarchical scattering centers.

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High Thermoelectric Performance in Non‐Toxic Earth‐Abundant Copper Sulfide

Cited by 678 publications

References 34 publications

Reversible structure manipulation by tuning carrier concentration in metastable Cu ₂ S

Reversible structure manipulation by tuning carrier concentration in metastable Cu ₂ S

Research Update: Cu–S based synthetic minerals as efficient thermoelectric materials at medium temperatures

Enhancing the Figure of Merit of Heavy‐Band Thermoelectric Materials Through Hierarchical Phonon Scattering

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High Thermoelectric Performance in Non‐Toxic Earth‐Abundant Copper Sulfide

Cited by 678 publications

References 34 publications

Reversible structure manipulation by tuning carrier concentration in metastable Cu 2 S

Reversible structure manipulation by tuning carrier concentration in metastable Cu 2 S

Research Update: Cu–S based synthetic minerals as efficient thermoelectric materials at medium temperatures

Enhancing the Figure of Merit of Heavy‐Band Thermoelectric Materials Through Hierarchical Phonon Scattering

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Reversible structure manipulation by tuning carrier concentration in metastable Cu ₂ S

Reversible structure manipulation by tuning carrier concentration in metastable Cu ₂ S