Thermoelectric properties of [Ca2CoO3−δ][CoO2]1,62 as a function of Co/Ca defects and Co3O4 inclusions

Büttner, G.; Populoh, Sascha; Xie, Wenjie; Trottmann, Matthias; Hertrampf, Jan; Döbeli, M.; Karvonen, Lasse; Yoon, Songhak; Thiel, Philipp; Niewa, Rainer; Weidenkaff, Anke

doi:10.1063/1.4984067

Cited by 9 publications

(6 citation statements)

References 47 publications

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“…The estimated errors in all cases were found to be <3% (~0.03 g/cm 3 ). Whenever possible, the ρ exp values were compared to the theoretical density ( ρ th ) values of the respective composites, calculated from the sum of the products of the theoretical densities of the reference intensity ratio-estimated phases (from X-Ray Diffraction analyses) and their respective amounts, in each case, i.e., by a simple mixing rule, using the following theoretical density values: ρ th (Ca 3 Co 4 O 9 ) = 4.69 g/cm 3 , from [ 50 ] and PDF card #04-016-0860; ρ th (Ca 3 Co 2 O 6 ) = 4.5 g/cm 3 , from PDF cards #00-051-0311 [ 51 ] and #04-010-0812; ρ th (CoO) = 6.58 g/cm 3 , from PDF card #04-005-4395.…”

Section: Methodsmentioning

confidence: 99%

Prospects for Electrical Performance Tuning in Ca3Co4O9 Materials by Metallic Fe and Ni Particles Additions

et al. 2021

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This work further explores the possibilities for designing the high-temperature electrical performance of the thermoelectric Ca3Co4O9 phase, by a composite approach involving separate metallic iron and nickel particles additions, and by employing two different sintering schemes, capable to promote the controlled interactions between the components, encouraged by our recent promising results obtained for similar cobalt additions. Iron and nickel were chosen because of their similarities with cobalt. The maximum power factor value of around 200 μWm−1K−2 at 925 K was achieved for the composite with the nominal nickel content of 3% vol., processed via the two-step sintering cycle, which provides the highest densification from this work. The effectiveness of the proposed approach was shown to be strongly dependent on the processing conditions and added amounts of metallic particles. Although the conventional one-step approach results in Fe- and Ni-containing composites with the major content of the thermoelectric Ca3Co4O9 phase, their electrical performance was found to be significantly lower than for the Co-containing analogue, due to the presence of less-conducting phases and excessive porosity. In contrast, the relatively high performance of the composite with a nominal nickel content of 3% vol. processed via a two-step approach is related to the specific microstructural features from this sample, including minimal porosity and the presence of the Ca2Co2O5 phase, which partially compensate the complete decomposition of the Ca3Co4O9 matrix. The obtained results demonstrate different pathways to tailor the phase composition of Ca3Co4O9-based materials, with a corresponding impact on the thermoelectric performance, and highlight the necessity of more controllable approaches for the phase composition tuning, including lower amounts and different morphologies of the dispersed metallic phases.

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Section: Methodsmentioning

confidence: 99%

Prospects for Electrical Performance Tuning in Ca3Co4O9 Materials by Metallic Fe and Ni Particles Additions

et al. 2021

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“…Some additional insights on the observed difference in phase composition between the 1ST and 2ST sintered samples can be obtained by analyzing the densities of the prepared ceramic materials ( Table 1). The relative density of the 1ST samples was calculated by assuming a simple mixing rule and the theoretical densities of 4.69 and 6.06 g/cm 3 for Ca 3 Co 4 O 9 and Co 3 O 4 , correspondingly [58]. The density shows a noticeable improvement for the 3Co_1ST samples, as compared to the pure matrix; the values for 6Co_1ST and 9Co_1ST are also slightly higher than for the reference, but slightly lower than for 3Co_1ST.…”

Section: Microstructural Evolutionmentioning

confidence: 97%

Redox-Promoted Tailoring of the High-Temperature Electrical Performance in Ca3Co4O9 Thermoelectric Materials by Metallic Cobalt Addition

et al. 2020

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This paper reports a novel composite-based processing route for improving the electrical performance of Ca3Co4O9 thermoelectric (TE) ceramics. The approach involves the addition of metallic Co, acting as a pore filler on oxidation, and considers two simple sintering schemes. The (1-x)Ca3Co4O9/xCo composites (x = 0%, 3%, 6% and 9% vol.) have been prepared through a modified Pechini method, followed by one- and two-stage sintering, to produce low-density (one-stage, 1ST) and high-density (two-stage, 2ST) ceramic samples. Their high-temperature TE properties, namely the electrical conductivity (σ), Seebeck coefficient (α) and power factor (PF), were investigated between 475 and 975 K, in air flow, and related to their respective phase composition, morphology and microstructure. For the 1ST case, the porous samples (56%–61% of ρth) reached maximum PF values of around 210 and 140 μWm−1·K−2 for the 3% and 6% vol. Co-added samples, respectively, being around two and 1.3 times higher than those of the pure Ca3Co4O9 matrix. Although 2ST sintering resulted in rather dense samples (80% of ρth), the efficiency of the proposed approach, in this case, was limited by the complex phase composition of the corresponding ceramics, impeding the electronic transport and resulting in an electrical performance below that measured for the Ca3Co4O9 matrix (224 μWm−1·K−2 at 975K).

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“…To understand the origin of the FDO and SDO time evolution in our case, we simulated the grating's temporal evolution of the charge carrier kinetics according to the rate equation (1). The D, k 1 , k 2 and k 3 coefficients are known for valence excitation [20,35,36], but the EUV excitation (preor post-edge) creates charge carriers with widely different kinetic energy distributions, whose behavior cannot be described using the coefficients for valence excitation. The time scale of relevance where these coefficients are operative is limited to 10 ps.…”

Section: Discussionmentioning

confidence: 99%

Separation of kinetic rate orders in extreme ultraviolet transient grating spectroscopy

Marroux,

Polishchuk,

Cannelli

et al. 2024

J. Phys. B: At. Mol. Opt. Phys.

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We present an Extreme Ultraviolet (EUV) transient grating (TG) experiment of the spinel Co3O4 compound using tuneable incident energies across the Co M2,3-edge and a 395 nm probe pulse, detecting both the first and the second diffraction orders. While the first diffraction order shows a monotonous behaviour as a function of time, with a sharp response at t=0, followed by a weak sub-picosecond component and a nearly constant signal thereafter, the time dependence of second diffraction order varies dramatically with the incident energy as it is tuned across the Co M-edge, with the appearance of a component at t>1 ps that grows with increasing energy. The results are rationalised in terms of the deviations of the initial grating from sinusoidal to non-sinusoidal, namely a flattening of the grating pattern, that introduces new Fourier components. These deviations are due to higher order, three-body terms in the population relaxation kinetics. These results highlight the use of the response of the second diffraction order in EUV TG as a tool to identify higher order terms in the population kinetics.

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Thermoelectric properties of [Ca2CoO3−δ][CoO2]1,62 as a function of Co/Ca defects and Co3O4 inclusions

Cited by 9 publications

References 47 publications

Prospects for Electrical Performance Tuning in Ca3Co4O9 Materials by Metallic Fe and Ni Particles Additions

Prospects for Electrical Performance Tuning in Ca3Co4O9 Materials by Metallic Fe and Ni Particles Additions

Redox-Promoted Tailoring of the High-Temperature Electrical Performance in Ca3Co4O9 Thermoelectric Materials by Metallic Cobalt Addition

Separation of kinetic rate orders in extreme ultraviolet transient grating spectroscopy

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