Electronic structure of the Ca<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>9</mml:mn></mml:msub></mml:math>compound from<i>ab initio</i>local interactions

Soret, Julien; Lepetit, Marie-Bernadette

doi:10.1103/physrevb.85.165145

Cited by 33 publications

(35 citation statements)

References 51 publications

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“…However, the t in misfits and Na x CoO 2 is much smaller than the value (130 meV) estimated by band calculation in Na x CoO 2 2 implying strong electron correlation, which is consistent with rather large γ 20, 29. This very small t value might come from disorder within the separating planes 45.…”

Section: Hall Effect As a Probe Of The Thermoelectric Properties Inmentioning

confidence: 54%

From oxides to selenides and sulfides: The richness of the CdI₂ type crystallographic structure for thermoelectric properties

Hébert

Kobayashi

Muguerra

et al. 2012

Physica Status Solidi (a)

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In this paper, we show how the thermoelectric properties can be modified in crystallographic structures based on the CdI 2 type layer, by changing the block layers between these CdI 2 type layers or by going from oxides to selenides and sulfides. In the case of oxides, the unique properties generated in these structures will be demonstrated in Bi-based misfit compounds. By combining Hall effect, resistivity, and Seebeck coefficients in single crystals of this family, the importance of doping and of spin and orbital degeneracy term on the Seebeck coefficient will be shown. From this single crystal investigation, the power factor at 300 K is found to be unexpectedly constant as a function of doping. To further enhance the power factor and thus ZT, it is necessary to modify either the block layer or to perform anionic substitutions. By going from oxides to selenides and sulfides, the decrease of the ionic character can induce a decrease of electrical resistivity. Compared to oxides, the properties can generally be described in a more classical way using Boltzmann transport theory. For these materials, the critical parameter is then thermal conductivity and this quantity can be decreased as shown here by intercalating Cu between the layers (Cu x TiS 2 ), or by making solid solution such as TiS 2 À x Se x . These two approaches will be described here, leading to ZT close to 0.5 and 0.4, at 800 and 700 K, respectively.

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Section: Hall Effect As a Probe Of The Thermoelectric Properties Inmentioning

confidence: 54%

From oxides to selenides and sulfides: The richness of the CdI₂ type crystallographic structure for thermoelectric properties

Hébert

Kobayashi

Muguerra

et al. 2012

Physica Status Solidi (a)

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“…The CdI 2 ‐type CoO 2 subcells, in which electrons are strongly correlated, serve as electronic transport layers to achieve the large Seebeck coefficient and low electrical resistivity, whereas the distorted rock‐salt‐type Ca 2 CoO 3 subcells enhance phonon scattering to achieve low thermal conductivity . In general, the unusual TE response may involve spin and orbital degeneracies (configurational entropy), spin and charge frustrations, enhanced effective mass in the vicinity of Mott metal‐insulator transition, or strong electronic correlations …”

Section: Introductionmentioning

confidence: 99%

Enhanced Thermoelectric Properties in Cu‐Doped c‐Axis‐Oriented Ca₃Co₄O_9+δ Thin Films

et al. 2013

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Transport properties of the good thermoelectric misfit oxide Ca3Co4O9 are examined. In-plane resistivity and Hall resistance measurements were made on epitaxial thin films which were grown on c-cut sapphire substrates using the pulsed laser deposition technique. Interpretation of the in-plane transport experiments relates the substrate-induced strain in the resulting film to single crystals under very high pressure (∼ 5.5 GPa) consistent with a key role of strong electronic correlation. They are confirmed by the measured high temperature maxima in both resistivity and Hall resistance. While hole-like charge carriers are inferred from the Hall effect measurements over the whole investigated temperature range, the Hall resistance reveals a non monotonic behavior at low temperatures that could be interpreted with an anomalous contribution. The resulting unconventional temperature dependence of the Hall resistance seems thus to combine high temperature strongly correlated features above 340 K and anomalous Hall effect at low temperature, below 100 K. Good thermoelectric materials, 1,2 which convert heat into electricity and vice versa, should have high figures of merit (ZT) where ZT= S 2 T/ρκ, so S (the thermoelec-tric power or Seebeck coefficient) should be large while ρ (resistivity) and κ (thermal conductivity) should be small at a temperature T. In addition to these properties , these materials should be physically and chemically robust for high temperature processes such as the generation of energy from waste heat, and therefore, oxides such as Na x CoO 2 and Ca 3 Co 4 O 9 have been received a considerable attention recently. 3,4 Among the oxides Ca 3 Co 4 O 9 is very promising because of its high room temperature (RT) thermopower (125 µV/K), low resistivity (12 mΩ cm), low thermal conductivity (30 mW (cm K) −1), and resistance to humidity. 4,5 Ca 3 Co 4 O 9 is a misfit oxide and can be denoted as [Ca 2 CoO 3 ] RS [CoO 2 ] 1.62 to recognize the incommensu-rate nature of the structure. The structure is composed of alternating layers of a distorted Ca 2 CoO 3 rock salt-like layer (RS) and a CoO 2 cadmium iodide-like layer which are stacked in the c-axis direction. Crystallographically , these two layers have similar a, c, and β lattice parameters but different b lattice parameters. The ratio of the b parameters for the Ca 2 CoO 3 layer to CoO 2 layer is 1.62. The material's anisotropic behavior is easily seen through the comparison of the in-plane and out-of-plane resistivity behavior (metallic versus semiconduct-ing, respectively). 4 Thus, to attain the highest properties in a thermoelectric device, growth along the c-axis would be best to insure uniform properties. The bulk can be magnetically aligned along the c-axis at high temperature, 6,7 but the thin films form provides a more convenient method for manufacturing useful thermoelec-tric devices. For this reason, we have undertaken the synthesis of Ca 3 Co 4 O 9 films on Al 2 O 3 (c-cut sapphire) substrates. 8 The resulting epitaxial film has thermoelec-tric ...

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“…4,5 However, most of the previous works in Ca 3 Co 4 O 9 system mainly focused on the enhancement of the room-or high-temperature TE performance. 6,7 The lowtemperature TE performance has not yet been investigated systematically, especially the low-temperature thermopower, which is considered to be in favor of the low-temperature TE refrigeration.…”

mentioning

confidence: 99%

Renormalized bands and low-temperature colossal thermopower induced by Ir doping in Ca3Co4O9 system

Huang¹,

Zhao²,

Lin³

et al. 2013

Journal of Applied Physics

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The effects of Ir doping on the low-temperature thermal and electrical transport properties of Ca3Co4−xIrxO9 (0 ≤ x ≤ 0.4) have been investigated. As Ir ions are doped into the system, a low-temperature thermopower upturn is introduced, and the temperature corresponding to the minimum thermopower TSmin increases monotonously with increasing x. Moreover, a low-temperature colossal thermopower is observed in the Ir-doped samples, which is beneficial to the low-temperature thermoelectric refrigeration in superconducting devices. For the x = 0.4 sample, its maximum thermopower Smax at the lowest measured temperature ∼24 K reaches 1500 μV/K. The appearance of such a colossal thermopower phenomenon is suggested to be closely related to the variations of the transport mechanism and the band structure induced by 5d-Ir doping.

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Electronic structure of the Ca3Co4O9compound fromab initiolocal interactions

Cited by 33 publications

References 51 publications

From oxides to selenides and sulfides: The richness of the CdI₂ type crystallographic structure for thermoelectric properties

From oxides to selenides and sulfides: The richness of the CdI₂ type crystallographic structure for thermoelectric properties

Enhanced Thermoelectric Properties in Cu‐Doped c‐Axis‐Oriented Ca₃Co₄O_9+δ Thin Films

Renormalized bands and low-temperature colossal thermopower induced by Ir doping in Ca3Co4O9 system

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Electronic structure of the Ca3Co4O9compound fromab initiolocal interactions

Cited by 33 publications

References 51 publications

From oxides to selenides and sulfides: The richness of the CdI2 type crystallographic structure for thermoelectric properties

From oxides to selenides and sulfides: The richness of the CdI2 type crystallographic structure for thermoelectric properties

Enhanced Thermoelectric Properties in Cu‐Doped c‐Axis‐Oriented Ca3Co4O9+δ Thin Films

Renormalized bands and low-temperature colossal thermopower induced by Ir doping in Ca3Co4O9 system

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Product

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From oxides to selenides and sulfides: The richness of the CdI₂ type crystallographic structure for thermoelectric properties

From oxides to selenides and sulfides: The richness of the CdI₂ type crystallographic structure for thermoelectric properties

Enhanced Thermoelectric Properties in Cu‐Doped c‐Axis‐Oriented Ca₃Co₄O_9+δ Thin Films