Na3Cu4S4-ein Thiocuprat mit unverknüpften 1
 ∞[Cu4S4] -Ketten / Na3Cu4S4-a Thiocuprate with Isolated 1
 ∞[Cu4S4]-Chains

Burschka, Christian

doi:10.1515/znb-1979-0308

Cited by 48 publications

(13 citation statements)

References 2 publications

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“…T h e m a t e r i a l c a n b e f o r m u l a t e d a s [(Cu 1+ ) 5 (Sn 4+ ) 2 (Te 2− ) 7 ](p + ). This situation is similar to that found in CuS, 61,62 NaCu 4 S 4 , 23 or Na 3 Cu 4 S 4 , 3,63 where all are well-known p-type metallic mixed-valence compounds. To further validate the nature of mixed valency several studies including spectroscopic (XPS), physical properties (electronic conductivity, Seebeck, and Hall effect), and electronic band structure calculations were undertaken.…”

Section: ■ Experimental Sectionsupporting

confidence: 84%

Metallic Ternary Telluride with Sphalerite Superstructure

Adhikary¹,

Mohapatra²,

Lee³

et al. 2016

Inorg. Chem.

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A new ternary compound with composition Cu5Sn2Te7 has been synthesized using the stoichiometric reaction of Cu, Sn, and Te. The compound crystallizes in C2 space group with unit cell parameters of a = 13.549(2) Å, b = 6.0521(11) Å, c = 9.568(2) Å, and β = 98.121(2)°. Cu5Sn2Te7 is a superstructure of sphalerite and exhibits tetrahedral coordination of Cu, Sn, and Te atoms, containing a unique adamantane-like arrangement. The compound is formally mixed valent with a high electrical conductivity of 9.8 × 10(5) S m(-1) at 300 K and exhibits metallic behavior having p-type charge carriers as indicated from the positive Seebeck coefficient. Hall effect measurements further confirm holes as charge carriers with a carrier density of 1.39 × 10(21) cm(-3) and Hall mobility of 4.5 cm(2) V(-1) s(-1) at 300 K. The electronic band structure calculations indicate the presence of a finite density of states around the Fermi level and agree well with the p-type metallic conductivity. Band structure analysis suggests that the effective mass of the hole state is small and could be responsible for high electronic conductivity and Hall mobility. The high thermal conductivity of 15.1 W m(-1) K(-1) at 300 K coupled with the low Seebeck coefficient results in a poor thermoelectric figure of merit (ZT) for this compound. Theoretical calculations indicate that if Cu5Sn2Te7 is turned into a valence precise compound by substituting one Cu by a Zn, a semiconducting material, Cu4ZnSn2Te7, with a direct band gap of ∼ 0.5 eV can be obtained.

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Section: ■ Experimental Sectionsupporting

confidence: 84%

Metallic Ternary Telluride with Sphalerite Superstructure

Adhikary¹,

Mohapatra²,

Lee³

et al. 2016

Inorg. Chem.

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“…These compounds host phase transitions, modulated superlattices, , and massive copper vacancies , and are of interest in energy harvesting and conversion, including but not limited to solid-state supercapacitors , and ionic conductors . All structural dimensionalities are found in this class, for example, the one-dimensional (1D) Na 3 Cu 4 S 4 , , the two-dimensional (2D) ACu 4 Q 3 (A = Na, K, Rb, Cs, Tl; Q = S, Se), , NaCu 4 S 4 , A 4 Cu 8 Te 10 (A = Rb, Cs), NaCu 6 Se 4 , and TlCu 2 Se 2 , and the three-dimensional (3D) K 4 Cu 8 Te 11 and Cs 3 Cu 20 Te 13 , to name a few. Generally, they can be classified by the electronic structures and have two different general categories: mixed-valent and valence-precise compounds.…”

Section: Introductionmentioning

confidence: 99%

High Hole Mobility and Nonsaturating Giant Magnetoresistance in the New 2D Metal NaCu₄Se₄ Synthesized by a Unique Pathway

et al. 2018

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The new compound NaCu4Se4 forms by the reaction of CuO and Cu in a molten sodium polyselenide flux, with the existence of CuO being unexpectedly critical to its synthesis. It adopts a layered hexagonal structure (space group P63/mmc with cell parameters a = 3.9931(6) Å and c = 25.167(5) Å), consisting of infinite two-dimensional (2D) [Cu4Se4]  slabs separated by Na + cations. X-ray photoelectron spectroscopy suggests that NaCu4Se4 is mixed-valent with the formula (Na +)(Cu +)4(Se 2)(Se )(Se2) 2. NaCu4Se4 is a p-type metal with a carrier density of ~10 21 cm-3 and a high hole mobility of ~808 cm 2 V-1 s-1 at 2 K based on electronic transport measurements. First-principles calculations suggest the density of states around the Fermi level are composed of Cud and Se-p orbitals. At 2 K, a very large transverse magnetoresistance of ~1400% was observed, with a nonsaturating, linear dependence on field up to 9 T. Our results indicate that the use of metal oxide chemical precursors can open reaction paths to new low-dimensional compounds.

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“…Among the many known copper chalcogenides are several unusual phases that feature monochalcogenides with a −1 charge without formation of chalcogen–chalcogen bonds. These occur in ternary (e.g., ACu 4 Q 3 (A = K, Rb, Cs, and Tl; Q = S and Se), − TlCu 2 Q 2 (Q = S and Se), Na 3 Cu 4 S 4 , , NaCu 6 Se 4 , and K 2 Cu 5 Te 5 ) and quaternary (e.g., K 2 Cu 2 CeS 4 , CsCuCeS 3 , K 2 Cu 2 Sn 2 S 6 , KCuS 4 , and K 6 Cu 12 U 2 S 15 ) systems. In the past, when many of these phases were discovered, the presumption was that the mixed valency had arisen because of the Cu 2+ /Cu + states .…”

Section: Introductionmentioning

confidence: 99%

Mixed-Valent NaCu₄Se₃: A Two-Dimensional Metal

et al. 2016

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The new ternary copper selenide NaCu4Se3 crystallizes in the RbCd4As3 structure type with the trigonal space group R3̅m and lattice constants a = 4.0316(4) Å and c = 31.438(8) Å. Its structure is built from two-dimensional slabs of (2)/∞[Cu4Se3] separated by Na(+) cations. The compound is formally mixed-valent with Se(2-)/Se(-) atoms and exhibits metallic properties. It is a hole conductor with an electrical conductivity of ∼300 S cm(-1) at room temperature and a thermopower of ∼10 μV K(-1). Hall effect measurements indicate holes as the dominant carrier with a concentration of ∼6.12(1) × 10(21) cm(-3) at 300 K. Density functional theory electronic structure calculations indicate p-type metallic behavior for the (2)/∞[Cu4Se3] framework, which is in a good agreement with the experimental metallic conductivity and Pauli paramagnetism.

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Na₃Cu₄S₄-ein Thiocuprat mit unverknüpften ¹ _∞[Cu₄S₄] -Ketten / Na₃Cu₄S₄-a Thiocuprate with Isolated ¹ _∞[Cu₄S₄]-Chains

Cited by 48 publications

References 2 publications

Metallic Ternary Telluride with Sphalerite Superstructure

Metallic Ternary Telluride with Sphalerite Superstructure

High Hole Mobility and Nonsaturating Giant Magnetoresistance in the New 2D Metal NaCu₄Se₄ Synthesized by a Unique Pathway

Mixed-Valent NaCu₄Se₃: A Two-Dimensional Metal

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Na3Cu4S4-ein Thiocuprat mit unverknüpften 1 ∞[Cu4S4] -Ketten / Na3Cu4S4-a Thiocuprate with Isolated 1 ∞[Cu4S4]-Chains

Cited by 48 publications

References 2 publications

Metallic Ternary Telluride with Sphalerite Superstructure

Metallic Ternary Telluride with Sphalerite Superstructure

High Hole Mobility and Nonsaturating Giant Magnetoresistance in the New 2D Metal NaCu4Se4 Synthesized by a Unique Pathway

Mixed-Valent NaCu4Se3: A Two-Dimensional Metal

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Product

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About

Na₃Cu₄S₄-ein Thiocuprat mit unverknüpften ¹ _∞[Cu₄S₄] -Ketten / Na₃Cu₄S₄-a Thiocuprate with Isolated ¹ _∞[Cu₄S₄]-Chains

High Hole Mobility and Nonsaturating Giant Magnetoresistance in the New 2D Metal NaCu₄Se₄ Synthesized by a Unique Pathway

Mixed-Valent NaCu₄Se₃: A Two-Dimensional Metal