Chemical manipulation of phase stability and electronic behavior in Cu4−xAgxSe2

Olvera, Alan; Bailey, Trevor P.; Uher, Ctirad; Poudeu, Pierre F. P.

doi:10.1039/c8ta01531g

Cited by 15 publications

(28 citation statements)

References 49 publications

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“…As can be seen, Cu1.982Bi0.006Se has the best TE properties within the near-room-temperature range among all the samples, which realizes a zTmax of ~ 0.43 at 373 K with an average zT of ~ 0.33 between 300 K and 373 K, showing a great enhancement compared to the undoped sample. This average zT is comparable with some of previous studies [37,47,55], as shown in Fig. S4.…”

Section: Resultssupporting

confidence: 92%

“…However, this observation will not be concerned because it is not the scope of this study, herein, only the properties of α-phases at near-room-temperature are discussed. Monotonous changes of both σ and S are observed, indicating that all the samples are typical p-type (positive S) degenerated semi-conductors due to the intrinsic Cu deficiencies [45,47,54,55]. With increasing Bi content, the σ decreases when x = 0.006 and increase when x > 0.006, while the S shows the reverse tendency.…”

Section: Resultsmentioning

confidence: 90%

“…Due to the relatively large band gap of α-Cu2Se (~ 1.23 eV) [37], the minor carriers (electrons) should not be excited at near-room-temperature, the hole concentration of the samples could stay stable before phase transition [47,54,55]. Therefore, only roomtemperature n values have been measured.…”

Section: Resultsmentioning

confidence: 99%

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Realizing Bi-doped α-Cu2Se as a promising near-room-temperature thermoelectric material

Liao

Yang

Chen

et al. 2019

Chemical Engineering Journal

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 90%

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Realizing Bi-doped α-Cu2Se as a promising near-room-temperature thermoelectric material

Liao

Yang

Chen

et al. 2019

Chemical Engineering Journal

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“…Their excellent thermoelectric properties have stimulated substantial efforts in searching for similar liquid-like materials. 38,39 While Cu 2 Se and CuAgSe show high ZT only above 600 K, Ag 2 Se, a n-type chalcogenide belonging to the same class of liquid-like materials, is a promising candidate for room temperature applications. Ag 2 Se has similarities with Cu 2 Se and CuAgSe in that all of these materials become superionic above their phase transition temperature (i.e., ∼400 K for Cu 2 Se, 29 ∼470 K for CuAgSe, 31 and ∼407 K for Ag 2 Se).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Furthermore, cation−cation substitution has been shown to promote phase stability in liquid-like compounds, such as in Cu 2 Se 63,64 and Cu 4−x Ag x Se 2 . 39 This motivated us to also investigate the impact of Cu substitution on the microstructure and thermoelectric properties of (Ag 1−x Cu x ) 2 SeS 0.01 (x = 0.01, 0.05, 0.1).…”

Section: ■ Introductionmentioning

confidence: 99%

Temperature-Dependent Structural Variation and Cu Substitution in Thermoelectric Silver Selenide

Jood

Ohta

2020

ACS Appl. Energy Mater.

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Ag 2 Se is a narrow band gap semiconductor with glass-like thermal conductivity which makes it attractive for room temperature thermoelectric applications. However, its structural stability is strongly affected by compositional changes, which have led to difficulty in tuning the transport properties in the past. Here, we investigated the temperature-dependent structural stability of stoichiometric Ag 2 Se and its minute anion excess counterpart, Ag 2 SeS 0.01 , from room temperature up to the transition temperature (where low-temperature orthorhombic phase changes to high-temperature cubic phase at ∼407 K). The metastable structure, which is formed to compensate for the instability of the main orthorhombic structure in Ag 2 Se, was found to exist in the entire temperature range studied. However, no metastable structure was formed in the Ag 2 SeS 0.01 sample, proving that minute anion excess is capable of stabilizing the orthorhombic structure throughout the temperature range of interest (300−400 K). The effect of Cu substitution on the thermoelectric properties of Ag 2 SeS 0.01 was also investigated, and it was found that 1% Cu substitution ((Ag 0.99 Cu 0.01 ) 2 SeS 0.01 ) enhances carrier mobility and carrier concentration, compared to that for Ag 2 SeS 0.01 and Ag 2 Se. As a result, up to 18% enhancement in S 2 /ρ (∼2.6 mW m −1 K −2 at 300 K and ∼2.8 mW m −1 K −2 at 375 K) was achieved compared to that of the non-Cu-substituted samples. The ZT (0.7 at 300 K), however, could not be improved compared to that of Ag 2 SeS 0.01 (0.8 at 300 K) but remained higher than that of Ag 2 Se (0.5 at 300 K), due to the increase in electronic contribution to thermal conductivity .

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Effect of ball milling time on the formation and thermal properties of Ag2Se and Cu2Se compounds

Tarani

Stathokostopoulos

Karfaridis

et al. 2023

J Therm Anal Calorim

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The thermoelectric materials community has made significant progress on nanostructured and processable materials to improve efficiency and flexibility, reducing manufacturing costs. Selenide compounds, such as Ag2Se and Cu2Se, have received a lot of attention because of their promising capabilities in thermoelectric applications. Additionally, Se is significantly more abundant than Te, with approximately ten times higher availability. High-energy ball milling (HEBM) process is a powerful solid-state synthesis/powder mechanical alloying method. The objective of this work is to form selenide compounds at different milling times (1–20 h) by HEBM process. The structural characterization of the compounds was studied by X-ray Diffraction and X-ray Photoelectron Spectroscopy, while the thermal stability of the prepared samples was examined by Thermogravimetric Analysis. The experimental results show that the Ag2Se sample synthesized at 20 h presents lower thermal stability because of the higher specific surface area and the increased porosity as a result of the hardening effect. Additionally, Cu2Se presents Cu2O(SeO3) as the main phase at low temperatures, while at higher temperatures, CuO is the dominant phase. Therefore, as the heating temperature increases, there is a complete evaporation of Se and a conversion of the remaining copper into copper oxide. The present study demonstrates a simple method for the synthesis of Ag2Se and Cu2Se thermoelectric materials with high oxidation resistance.

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Chemical manipulation of phase stability and electronic behavior in Cu_4−xAg_xSe₂

Abstract: Gradual stoichiometric chemical substitution of Cu by Ag in the p-type Cu2Se phase enables phase segregation and incremental switching of the electronic transport to n-type behavior for large Ag/Cu ratios.

Cited by 15 publications

References 49 publications

Realizing Bi-doped α-Cu2Se as a promising near-room-temperature thermoelectric material

Realizing Bi-doped α-Cu2Se as a promising near-room-temperature thermoelectric material

Temperature-Dependent Structural Variation and Cu Substitution in Thermoelectric Silver Selenide

Effect of ball milling time on the formation and thermal properties of Ag2Se and Cu2Se compounds

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