Phase transitions and transport properties of complex copper chalcogenides

Jacyna-Onyszkiewicz, I.; Sidowski, M.; Стародуб, В. А.; Robaszkiewicz, S.

doi:10.1002/pssa.200306404

Cited by 5 publications

(9 citation statements)

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“…Jacyna-Onyszkiewicz et al , briefly reported the temperature-dependent resistivity of KCu 3– x Se 2 and observed an interesting transition from semiconducting to metallic behavior at ∼160 K. However, the resistivity data contained several erratic steps, and their reproducibility was not discussed. The contact material in that case was not specified, but we observed similar irregular, nonreproducible behavior when Ag paste contacts were used on KCu 3– x Se 2 single crystals.…”

Section: Resultsmentioning

confidence: 99%

“…Although its crystal structure was unknown, Jacyna-Onyszkiewicz et al briefly reported its temperature-dependent resistivity. 23,24 These data contained unexplained anomalies that bore resemblance to charge-density-wave formation (e.g., as in TiSe 2 25 ) and thus warranted further study. Here we present the synthesis, crystal structure, and optical and electronic properties of KCu 3−x Se 2 .…”

Section: ■ Introductionmentioning

confidence: 96%

“…With regard to our interest in layered compounds with physical properties related to the A x Fe 2– x Se 2 ( A = alkali metal) superconductors, we discovered the ternary phase KCu 3– x Se 2 . Although its crystal structure was unknown, Jacyna-Onyszkiewicz et al briefly reported its temperature-dependent resistivity. , These data contained unexplained anomalies that bore resemblance to charge-density-wave formation (e.g., as in TiSe 2 ) and thus warranted further study. Here we present the synthesis, crystal structure, and optical and electronic properties of KCu 3– x Se 2 .…”

Section: Introductionmentioning

confidence: 99%

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Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu_3–xSe₂

et al. 2017

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The two-dimensional material KCu3–x Se2 was synthesized using both a K2Se3 flux and directly from the elements. It crystallizes in the CsAg3S2 structure (monoclinic space group C2/m with a = 15.417(3) Å, b = 4.0742(8) Å, c = 8.3190(17) Å, and β = 112.94(3)°), and single-crystal refinement revealed infinite copper-deficient [Cu3–x Se2]− layers separated by K+ ions. Thermal analysis indicated that KCu3–x Se2 melts congruently at ∼755 °C. UV–vis spectroscopy showed an optical band gap of ∼1.35 eV that is direct in nature, as confirmed by electronic structure calculations. Electronic transport measurements on single crystals yielded an in-plane resistivity of ∼6 × 10–1 Ω cm at 300 K that has a complex temperature dependence. The results of Seebeck coefficient measurements were consistent with a doped p-type semiconductor (S = +214 μV K–1 at 300 K), with doping being attributed to copper vacancies. Transport is dominated by low-mobility (on the order of 1 cm2 V–1 s–1) holes caused by relatively flat valence bands with substantial Cu 3d character and a significant concentration of Cu ion vacancy defects (p ∼ 1019 cm–3) in this material. Electronic band structure calculations showed that electrons should be significantly more mobile in this structure type.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu_3–xSe₂

et al. 2017

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“…With decreasing copper content the sulfur is oxidized, creating holes in the sulfur 3p band; thus non-stoichiometric KCu 7Àx S 4 exhibits metallic behavior and a metal-to-semimetal transition with increasing temperature. 20,[22][23][24] In copper chalcogenides Cu 2Àx X (X ¼ S, Se or Te), in spite of the obvious change in thermal conductivity k with the phase transition, there is little difference in resistivity. 10 Analogously, although an obvious change of k can be observed for both the KCu 7Àx S 4 and Cu 7 S 4 samples with increasing temperature, the sharp change in resistivity only occurs in the KCu 7Àx S 4 lm due to its metal-tosemimetal transition.…”

Section: Resultsmentioning

confidence: 99%

Introducing kalium into copper sulfide for the enhancement of thermoelectric properties

Kang

et al. 2013

J. Mater. Chem. A

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Advanced thermoelectric technology offers the potential to convert waste heat into useful electricity, and a mechanism of transmissionfree methods for solid state cooling. A low thermal conductivity is a prerequisite for obtaining high efficiency thermoelectric materials. It is a challenge to achieve low thermal conductivity without simultaneously destroying the electric conductivity, for which a 'phonon glass/liquid-electron crystal' is proposed. To realize the phonon glasselectron crystal, a host-guest cage crystal system is considered, while to realize the phonon liquid-electron crystal, superionic conductivity is needed. Here we report a novel material, a KCu 7Àx S 4 nanowire, which exhibits enhanced thermoelectric properties compared to the traditional chalcogenide Cu 7 S 4 nanostructure. The presence of K ions not only forms a clathrate and a superionic fluid structure, which provides the phonon glass and liquid-electron crystal, but also adjusts the product to give a nanowire-like morphology. A low thermal conductivity and large Seebeck coefficient can be achieved when the nanowires are pressed into a bulk material. Higher electrical conductivity is also obtained below 420 K. In addition, the numerous grain boundaries, Cu deficiency and the orientated nanowires further increase the thermoelectric properties. The results indicate a new strategy to obtain high efficiency thermoelectric materials by introducing kalium into copper chalcogenides to form a new crystal structure with 'phonon glass and liquid-electron crystal' properties.

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“…The compounds containing copper can be classified into two general categories, where Cu is either in valence precise or in a mixed valence state. It has been established that besides copper, the chalcogen present in the ternary systems also exhibit a mixed valence state 13,14 . Valence precise state compounds are reported to be semiconductors 15 while the mixed valence state compounds could be metals or superconductors 16 .…”

Section: Introductionmentioning

confidence: 99%

Exploring Exemplary Optoelectronic and Charge Transport Properties of KCuX(X=Se,Te)

Parveen

Vaitheeswaran

2018

Sci Rep

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We report the electronic structure, optical and charge transport properties of the unexplored ternary Zintl phases KCuX(X=Se,Te) from the first principles calculations employing the full-potential linearized augmented plane-wave (FLAPW) method with the Tran Blaha modified Becke-Johnson (TBmBJ) potential. It is demonstrated that the materials are direct band gap (1.13, 1.38 eV) semiconductors with covalent bonding between Cu and (Se/Te). The calculated low effective mass and high carrier mobility (over 105 cm2/V.s) accentuate that KCuX have good carrier transport and the materials may have possible applications in solar cell absorbers and nanoelectronic devices. Absorption spectra indicates that the ternary crystals are UV-A light absorbers and could be useful in photovoltaic and photodetector applications. A study on the effect of pressure (till 5 GPa) is carried out in order to further explore the materials for their electronic band gaps and charge transport properties as they are proposed to be useful in future contemporary electronic devices. It is observed that pressure enhances the intrinsic carrier mobility and thermal stability of KCuX, indicating that the materials can withstand robust external conditions.

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Phase transitions and transport properties of complex copper chalcogenides

Cited by 5 publications

References 0 publications

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu_3–xSe₂

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu_3–xSe₂

Introducing kalium into copper sulfide for the enhancement of thermoelectric properties

Exploring Exemplary Optoelectronic and Charge Transport Properties of KCuX(X=Se,Te)

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Phase transitions and transport properties of complex copper chalcogenides

Cited by 5 publications

References 0 publications

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu3–xSe2

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu3–xSe2

Introducing kalium into copper sulfide for the enhancement of thermoelectric properties

Exploring Exemplary Optoelectronic and Charge Transport Properties of KCuX(X=Se,Te)

Contact Info

Product

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Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu_3–xSe₂

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu_3–xSe₂