Exploratory Work in the Quaternary System of Ca–Eu–Cd–Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions

Ovchinnikov, Alexander; Darone, Gregory M.; Saparov, Bayrammurad; Bobev, Svilen

doi:10.3390/ma11112146

Cited by 15 publications

(10 citation statements)

References 47 publications

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“…This may have originated from the Bi 2 O 3 -rich powders or the oxidation of trace Bi powders during the synthesis process. Further lattice refinement of the XRD data reveals the expansion of lattice parameters (a, c) in Pb&Yb co-doped BiCuSeO with increasing dopants, as shown in Figure 1B, which is attributed to the larger ionic radius of Pb 2+ (1.19 Å) 27 and the similar ionic radius of Yb 2+/3+ (1.02 Å/ 0.87 Å) 28,29 in comparison with that of Bi 3+ (0.96 Å). 24 The XRD data demonstrate that Pb and Yb dopants have been incorporated into the lattices successfully substituting for Bi sites, and Pb&Yb co-doped BiCuSeO samples have been synthesized by a two-step reaction using BM and HPHT methods.…”

Section: Resultsmentioning

confidence: 86%

Synergistically Optimized Electron and Phonon Transport of Polycrystalline BiCuSeO via Pb and Yb Co-Doping

Yin

Liu

et al. 2021

ACS Appl. Mater. Interfaces

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Polycrystalline BiCuSeO is considered as a promising thermoelectric material due to its intrinsically low thermal conductivity and moderate Seebeck coefficient. However, its low electrical conductivity and coupled electron−phonon transport properties restrict the further improvement of the thermoelectric performance. In this work, Pb and Yb dopants are incorporated into BiCuSeO to substitute for Bi sites via ball milling and high-pressure and high-temperature sintering, leading to a synergistic optimization of the electron and phonon transport and improved thermoelectric performance. The carrier concentration exhibits an enhancement with increasing Pb&Yb co-doping contents. Meanwhile, the decreased carrier mobility is suppressed appropriately by coordinating with the interplay of Pb and Yb dopants on the electronic structure. Besides, Pb&Yb co-doping combined with high-pressure and high-temperature sintering introduces abundant grain boundaries, dislocations, and point defects to effectively decrease the lattice thermal conductivity by scattering phonons in a broad frequency range. Coupled with the synergistic optimization of the electrical and thermal properties, a maximum zT of 1.2 is achieved in Bi 0.88 Pb 0.06 Yb 0.06 CuSeO at 850 K, which significantly outperforms the majority of oxygen-containing thermoelectric materials. Our study suggests that dual doping of bivalent ions and rare-earth elements at Bi sites is an effective strategy for improving the thermoelectric performance of BiCuSeO.

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Section: Resultsmentioning

confidence: 86%

Synergistically Optimized Electron and Phonon Transport of Polycrystalline BiCuSeO via Pb and Yb Co-Doping

Yin

Liu

et al. 2021

ACS Appl. Mater. Interfaces

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“…Yb 2 CdSb 2 and other Zintl phases with the A 2 MPn 2 composition are of interest for thermoelectric (TE) applications because of their low thermal conductivity and high TE power factor. − These properties result in a high dimensionless figure of merit, zT = S 2 T /ρκ, where S is the Seebeck coefficient, ρ is the electrical resistivity, and κ is the thermal conductivity. TE materials are used to fabricate TE generators, which function by connecting a p-type leg and a n-type leg thermally in parallel and electrically in series across a temperature gradient.…”

Section: Introductionmentioning

confidence: 99%

Solid Solution Yb_2–xCa_xCdSb₂: Structure, Thermoelectric Properties, and Quality Factor

et al. 2021

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Solid solutions of Yb 2−x A x CdSb 2 (A = Ca, Sr, Eu; x ≤ 1) are of interest for their promising thermoelectric (TE) properties. Of these solid solutions, Yb 2−x Ca x CdSb 2 has end members with different crystal structures. Yb 2 CdSb 2 crystallizes in the polar space group Cmc2 1 , whereas Ca 2 CdSb 2 crystallizes in the centrosymmetric space group Pnma. Other solid solutions, Yb 2−x A x CdSb 2 (A = Sr, Eu), crystallize in the polar space group for x ≤ 1, and compositions with x ≥ 1 have not been reported. Both structure types are composed of corner-sharing CdSb 4 tetrahedra condensed into sheets that differ by the stacking of the layers. Single crystals of the solid solution Yb 2−x Ca x CdSb 2 (x = 0−1) were studied to elucidate the structural transition between the Yb 2 CdSb 2 and Ca 2 CdSb 2 structure types. For x ≤ 1, the structures remain in the polar space group Cmc2 1 . As the Ca content is increased, a positional disorder arises in the intralayer cation sites (Yb2/Ca2) and the Cd site, resulting in inversion of the CdSb 4 tetrahedral chain. This phenomenon could be indicative of an intergrowth of the opposing space group. The TE properties of polycrystalline samples of Yb 2−x Ca x CdSb 2 (x ≤ 1) were measured from 300 to 525 K. The lattice thermal conductivity is extremely low (0.3−0.4 W/m•K) and the Seebeck coefficients are high (100−180 μV/K) across the temperature range. First-principles calculations show a minimum in the thermal conductivity for the x = 0.3 composition, in good agreement with experimental data. The low thermal conductivity stems from the acoustic branches being confined to low frequencies and a large number of phonon scattering channels provided by the localized optical branches. The TE quality factor of the Yb 1.7 A 0.3 CdSb 2 (A = Ca, Sr, Eu) series has been calculated and predicts that the A = Ca and Sr solid solutions may not improve with carrier concentration optimization but that the Eu series is worthy of additional modifications. Overall, the x = 0.3 compositions provide the highest zT because they provide the best electronic properties with the lowest thermal conductivity.

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“…Among the methods used for single-crystal growth of intermetallic compounds, the so-called flux growth approach has gained notable recognition owing to its simplicity and adaptability (Kanatzidis et al, 2005;Phelan et al, 2012;Latturner, 2018;Wang et al, 2020). Typically utilized fluxes encompass low-melting metals, such as Zn, Cd, Al, Ga, In, Sn, Pb, and Bi (Hu et al, 2007;White et al, 2015;Janka et al, 2014;He et al, 2012;Verchenko et al, 2012;Childs et al, 2019;Ovchinnikov, Darone et al, 2018;Baranets, Darone et al, 2019;Baranets, Voss et al, 2019;Ovchinnikov & Bobev, 2019a;Motoyama et al, 2018). In some cases, liquid alloys, in particular eutectic mixtures, or congruently melting compounds are utilized (Stojanovic & Latturner, 2007;Tucker et al, 2012;Verchenko et al, 2019;Rhodehouse et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Electronic stabilization by occupational disorder in the ternary bismuthide Li_3–x–yIn_xBi (x ≃ 0.14, y ≃ 0.29)

Ovchinnikov

Bobev

2020

Acta Crystallogr C

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A ternary derivative of Li3Bi with the composition Li3–x–yInxBi (x ≃ 0.14, y ≃ 0.29) was produced by a mixed In+Bi flux approach. The crystal structure adopts the space group Fdm (No. 227), with a = 13.337 (4) Å, and can be viewed as a 2 × 2 × 2 superstructure of the parent Li3Bi phase, resulting from a partial ordering of Li and In in the tetrahedral voids of the Bi fcc packing. In addition to the Li/In substitutional disorder, partial occupation of some Li sites is observed. The Li deficiency develops to reduce the total electron count in the system, counteracting thereby the electron doping introduced by the In substitution. First‐principles calculations confirm the electronic rationale of the observed disorder.

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Exploratory Work in the Quaternary System of Ca–Eu–Cd–Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions

Cited by 15 publications

References 47 publications

Synergistically Optimized Electron and Phonon Transport of Polycrystalline BiCuSeO via Pb and Yb Co-Doping

Synergistically Optimized Electron and Phonon Transport of Polycrystalline BiCuSeO via Pb and Yb Co-Doping

Solid Solution Yb_2–xCa_xCdSb₂: Structure, Thermoelectric Properties, and Quality Factor

Electronic stabilization by occupational disorder in the ternary bismuthide Li_3–x–yIn_xBi (x ≃ 0.14, y ≃ 0.29)

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Exploratory Work in the Quaternary System of Ca–Eu–Cd–Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions

Cited by 15 publications

References 47 publications

Synergistically Optimized Electron and Phonon Transport of Polycrystalline BiCuSeO via Pb and Yb Co-Doping

Synergistically Optimized Electron and Phonon Transport of Polycrystalline BiCuSeO via Pb and Yb Co-Doping

Solid Solution Yb2–xCaxCdSb2: Structure, Thermoelectric Properties, and Quality Factor

Electronic stabilization by occupational disorder in the ternary bismuthide Li3–x–y In x Bi (x ≃ 0.14, y ≃ 0.29)

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Solid Solution Yb_2–xCa_xCdSb₂: Structure, Thermoelectric Properties, and Quality Factor

Electronic stabilization by occupational disorder in the ternary bismuthide Li_3–x–yIn_xBi (x ≃ 0.14, y ≃ 0.29)