Optical investigation of ytterbium monochalcogenides

Lashkarev, G. V.; Ivanchenko, L. A.; Paderno, Yu. B.

doi:10.1002/pssb.2220490150

Cited by 15 publications

(8 citation statements)

References 4 publications

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“…In SmSe there are two f-to-t 2g promotions at 1.03 and 1.85 eV, but there are no reports of intermetallic CT in heterovalent Sm x Se y . Related measurements on YbSe x are informative: in YbSe f 14 -to-f 13 t 2g 1 promotions were assigned at 2.05 and 3.0 eV, and a feature at 0.9 eV observed in nonstoichiometric samples was attributed to a Yb(II)−Yb(III) CT process . From these relative excitation energies it is reasonable to suggest that the 700 nm absorption for 1 is a f 6 -to-f 5 d 1 promotion.…”

Section: Discussionmentioning

confidence: 93%

“…These spectroscopic differences can be rationalized by noting that while Yb(SePh) 2 coordination compounds appear to be thermally stable in THF with respect to subsequent C−Se bond cleavage reactions, the analogous Sm(SePh) 2 compounds are unstable with respect to the formation of Sm(III) selenido clusters, 3a,e and so the structure of the Sm cluster is not maintained when the compound is dissolved in stronger Lewis base solvents. Analogous Ln(III)/Sm(II) compounds with redox inactive Ln(III) have not yet been successfully isolated, and so any assignment of the 700 nm (1.7 eV) transition as either an f 6 −f 5 d 1 promotion or a Sm(II)−Sm(III) CT excitation is tentatively based on data from solid-state literature. In SmSe there are two f-to-t 2g promotions at 1.03 and 1.85 eV, but there are no reports of intermetallic CT in heterovalent Sm x Se y .…”

Section: Discussionmentioning

confidence: 99%

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Heterovalent Clusters: Ln₄Se(SePh)₈ (Ln₄ = Sm₄, Yb₄, Sm₂Yb₂, Nd₂Yb₂)

et al. 1999

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The heterovalent (2 Ln2+, 2 Ln3+) tetranuclear (DME)4Ln4Se(SePh)8 clusters (Ln = Sm, Yb, Nd(III)/Yb(II), Sm(III)/Yb(II); DME = dimethoxyethane) can be prepared either by the reduction of Se−C bonds with Ln or by the reaction of Ln(SePh)2 with elemental Se in DME. The Sm(II) compound is difficult to isolate because it slowly redissolves after precipitation. The Yb4 compound and Nd2Yb2 compounds are considerably more stable, and can be isolated in higher yield. For the Ln = Sm4, Yb4, Sm2Yb2, and Nd2Yb2 clusters, low-temperature structural characterization reveals a square array of four metal ions with a crystallographically imposed disorder that renders the Ln(II) and Ln(III) sites indistinguishable; the Nd2Yb2 compound also crystallizes in a lattice-solvated unit cell in which there are distinct Ln(II)/Ln(III) metal ions. Connecting the four metals in all structures is a selenido ligand that caps the square array of Ln ions, and pairs of SePh ligands that bridge each of the four edges, with a chelating DME ligand saturating the primary coordination sphere of the seven-coordinate Ln ions. Yb-L3 X-ray absorption edge measurements on the disordered Yb4 cluster reveal a strong bimodal white line feature that clearly indicates the presence of both Yb(II) and Yb(III) ions. Magnetic susceptibility measurements on the Yb4 cluster indicate that the material is a static, inhomogeneous mixed valent material with well-defined Yb(II) and Yb(III) ions and a crossover in the Curie−Weiss behavior at low temperatures is interpreted in terms of crystal field and antiferromagnetic interactions. These small cluster fragments represent intermediates in the stepwise formation of larger clusters, i.e., dimerization of the Ln4 in a face-to-face arrangement gives the metal core of the now familiar octanuclear Ln8E6(EPh)12 clusters.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Heterovalent Clusters: Ln₄Se(SePh)₈ (Ln₄ = Sm₄, Yb₄, Sm₂Yb₂, Nd₂Yb₂)

et al. 1999

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“…For the structural family with the cation-defective Th 3 P 4 -type arrangement, see: Pardo et al (1963); Flahaut et al (1965); Lashkarev & Paderno (1965). For the rare-earth sesquiselenides M 2 Se 3 with M = La-Pr and Sm-Lu, see: Grundmeier & Urland (1995); Folchnandt (1997); Folchnandt & Schleid (2001); Folchnandt et al (2004).…”

Section: Related Literaturementioning

confidence: 99%

“…Comment C-type Nd 2 Se 3 ( Fig. 1) belongs to a structural family with the cation-defect Th 3 P 4 -type arrangement (Pardo et al, 1963;Flahaut et al, 1965;Lashkarev & Paderno, 1965) adopted by rare-earth sesquiselenides M 2 Se 3 with M = La -Pr and Sm -Lu (Grundmeier & Urland, 1995;Folchnandt, 1997;Folchnandt & Schleid, 2001;Folchnandt et al, 2004) following the general formula M 2.667 □ 0.333 Se 4 . The Nd 3+ cations occupy the 12a position, whereas selenium resides at the 16c position.…”

Section: C-type Nd 2 Sementioning

confidence: 99%

C-type Nd₂Se₃

2009

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The title compound, neodymium sesquiselenide, is isotypic with the other known rare-earth metal(III) selenides M 2Se3 (M = La–Pr and Sm–Lu) with the cubic C-type structure. It adopts a cation-defective Th3P4-type arrangement with close to 8/9 of the unique neodymium-cation site occupied, leading to the composition Nd2.667Se4 (Z = 4) or Nd2Se3 (Z = 5.333), respectively. The Nd3+ cations are thus surrounded by eight selenide anions, forming trigonal [NdSe8]13− dodecahedra, whereas the Se2− anions exhibit a sixfold coordination, but due to the under-occupation of neodymium, each one is statistically surrounded by only 5.333 cations. The crystal studied was a merohedral twin with a 0.31 (6):0.69 (6) domain ratio.

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“…For instance, the YbTmSb ternary phase in Yb 14Àx Tm x MnSb 11 YbTe is a p-type semiconductor, which may partially cancel out the Te doping effect. 34 This minor phase along with inhomogeneity as indicated in the Te microprobe image (Fig. 3) increases with the increasing intended amount of Te used in the synthesis and will contribute to the total thermal conductivity of the pellet.…”

Section: Transport Propertiesmentioning

confidence: 98%

Magnetic and transport properties of Te doped Yb14MnSb11

Abdusalyamova²,

Махмудов³

et al. 2012

J. Mater. Chem.

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A series of single crystal samples, Yb 14 MnSb 11Àx Te x (x # 0.2), were investigated via Sn flux. The element distributions were mapped using an electron microprobe, which demonstrated inhomogeneity and limited solubility of Te in the crystals. The magnetic properties of two crystals of compositions Yb 13.80(2) Mn 1.03(1) Sb 11.11(4) Te 0.06(3) and Yb 13.82(3) Mn 1.02(1) Sb 11.02(8) Te 0.14(6) were investigated. Increasing amounts of Te increase the saturation moment of Yb 14 MnSb 11Àx Te x , and slightly lower the ordering temperature T C by about 1 K. This is attributed to the filling of the hole in Yb 14 MnSb 11 and the reduction of the screening of the Mn 2+ d 5 electrons, resulting in a higher effective moment. Hotpressed, fully dense pellets of Yb 13.72(3) Mn 1.08(1) Sb 11.13(6) Te 0.07(5) , Yb 13.76(5) Mn 1.11(1) Sb 10.96(8) Te 0.16(8) , and Yb 13.76(4) Mn 1.10(2) Sb 10.95(9) Te 0.19(7) were prepared for thermoelectric property measurements. Both Seebeck coefficient and electrical resistivity increase with increasing amount of Te as a result of decreasing carrier concentration. Increasing amounts of YbTe with increasing x could be identified in the electron microprobe. The total thermal conductivity was approximately the same for all compositions, similar to that of Yb 14 MnSb 11 . The figure of merit zT reaches a maximum of 1.11 for x ¼ 0.07 at 1240 K, which is approximately 12% higher than the parent compound, Yb 14 MnSb 11 .

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Optical investigation of ytterbium monochalcogenides

Cited by 15 publications

References 4 publications

Heterovalent Clusters: Ln₄Se(SePh)₈ (Ln₄ = Sm₄, Yb₄, Sm₂Yb₂, Nd₂Yb₂)

Heterovalent Clusters: Ln₄Se(SePh)₈ (Ln₄ = Sm₄, Yb₄, Sm₂Yb₂, Nd₂Yb₂)

C-type Nd₂Se₃

Magnetic and transport properties of Te doped Yb14MnSb11

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Optical investigation of ytterbium monochalcogenides

Cited by 15 publications

References 4 publications

Heterovalent Clusters: Ln4Se(SePh)8 (Ln4 = Sm4, Yb4, Sm2Yb2, Nd2Yb2)

Heterovalent Clusters: Ln4Se(SePh)8 (Ln4 = Sm4, Yb4, Sm2Yb2, Nd2Yb2)

C-type Nd2Se3

Magnetic and transport properties of Te doped Yb14MnSb11

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Heterovalent Clusters: Ln₄Se(SePh)₈ (Ln₄ = Sm₄, Yb₄, Sm₂Yb₂, Nd₂Yb₂)

Heterovalent Clusters: Ln₄Se(SePh)₈ (Ln₄ = Sm₄, Yb₄, Sm₂Yb₂, Nd₂Yb₂)

C-type Nd₂Se₃