High-temperature thermoelectric properties of Na- and W-Doped Ca3Co4O9 system

Hira, Uzma; Han, Li; Norrman, Kion; Christensen, Dennis Valbjørn; Pryds, Nini; Sher, Falak

doi:10.1039/c8ra01691g

Cited by 25 publications

(19 citation statements)

References 59 publications

(79 reference statements)

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“…While in Ref. [9], Na and W dual doping in Ca 3 Co 4 O 9 system was claimed able to increase figure of merit value more than two times of the undoped sample at 1000 K. The crystal structure of Ca 3 Co 4 O 9 misfit-layered as shown in Fig. 1 consists of two layers (Ca 2 CoO 3 )(CoO 2 ) b 1 /b 2 .…”

Section: Introduction mentioning

confidence: 91%

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

2020

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Ca 3 Co 4 O 9 is a p-type semiconducting material that is well-known for its thermoelectric (TE), magnetic, electronic, and electro-optic properties. In this study, sol-gel autoignition was used to prepare Ca 3 Co 4 O 9 at different calcination temperatures (773, 873, 973, and 1073 K) and time (4, 6, 8, 10, 12, and 14 h) using starch as a fuel. The phase and microstructure of the prepared Ca 3 Co 4 O 9 powder were investigated. Thermogravimetry-differential thermal analysis (TGA) confirms that the final weight loss occurred at 1073 K to form Ca 3 Co 4 O 9 stable powder. The variable-pressure scanning electron microscopy (VP-SEM) images show that the size of powder particles increases from 1.15 to 1.47 μm as calcination time increases from 4 to 12 h, and the size remains almost constant thereafter. A similar pattern is also observed on the increment of the crystallite size and percentage of crystallinity with X-ray diffraction (XRD) analysis. The highest crystallinity is found about 92.9% when the powder was calcinated at 1073 K for 12 and 14 h with 458 and 460 Å crystallite size, respectively. Energy dispersive X-ray spectroscopy (EDS) analysis demonstrates that the calcinated powder has a high intensity of Ca, Co, and O with uniform distribution. High-resolution transmission electron microscopy (HRTEM) images prove that there is no distinct lattice distortion defect on the crystal structure.

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Section: Introduction mentioning

confidence: 91%

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

2020

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“…Timeline of the improvement in the ZT of Ca 3 Co 4 O 9+δ polycrystalline materials by the addition of different doping elements. ,,,,− *The ZT value of this work is also reported. The goal of reaching a ZT material over 1 for commercial applications would be achievable within a few years.…”

Section: Oxide Ceramics Outperforming the Single Crystalsmentioning

confidence: 86%

“…The goal of reaching a ZT material over 1 for commercial applications would be achievable within a few years. Table S3 − shows historical progression of the thermoelectric properties of Ca 3 Co 4 O 9+δ .…”

Section: Oxide Ceramics Outperforming the Single Crystalsmentioning

confidence: 99%

Thermoelectric Oxide Ceramics Outperforming Single Crystals Enabled by Dopant Segregations

et al. 2020

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Calcium cobaltite Ca 3 Co 4 O 9+δ in a single-crystal form was reported with an extrapolated dimensionless thermoelectric figure of merit of 0.87 in the year 2003. Regardless of the intensive effort during the past 2 decades, the performance of polycrystalline ceramics remained low and was reported to be only ∼30 to 60% of that found for single crystals. Here, for the first time, the designed nonstoichiometric Ca 3−x Tb x Co 4 O 9+δ Bi y ceramics with intragranular dopant substitution are introduced, where the undersized dopant of Tb depletes at the grain boundaries and the oversized Bi segregates at the grain boundaries. Such synergetic dopant distribution simultaneously increases the electrical conductivity and the Seebeck coefficient and results in the oxide ceramics with a peak ZT of 0.9, outperforming single crystals over a wide range of temperatures.

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“…These intrinsic requirements de ne the gure of merit (zT = α 2 σT /κ) for thermoelectric materials [1]. Developing new thermoelectric materials with higher performance, wider ranges of operating temperatures, and di erent chemical compatibilities are active areas of research [2][3][4][5][6][7][8][9][10]. SrTiO 3 is one such material being investigated-it has high power factors and is composed of earth-abundant, non-toxic elements.…”

Section: Introductionmentioning

confidence: 99%

Grain Boundary Engineering Nanostructured SrTiO₃ for Thermoelectric Applications

Dylla

Kuo

Witting

et al. 2019

Adv Materials Inter

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Nanostructuring to reduce thermal conductivity is among the most promising strategies for designing next-generation, high-performance thermoelectric materials. In practice, electrical grain boundary resistance can overwhelm the thermal conductivity reduction induced by nanostructuring, which results in worse overall performance. Since a large body of work has characterized the transport of both polycrystalline ceramics and single crystals of SrTiO 3 , it is an ideal material system for conducting a case study of electrical grain boundary resistance. An e ective mass model is used to characterize the transport signatures of electrical grain boundary resistance and evaluate thermodynamic design principles for controlling that resistance. Treating the grain boundary as a secondary phase to the bulk crystallites explains the transport phenomena. Considering that the interface can be engineered by controlling oxygen partial pressure, temperature, and the addition of extrinsic elements into the grain boundary phase, the outlook for SrTiO 3 as a nanostructured thermoelectric is promising, and the zT could be greater than 0.5 at room temperature.

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High-temperature thermoelectric properties of Na- and W-Doped Ca₃Co₄O₉ system

Abstract: The detailed crystal structures and high temperature thermoelectric properties of polycrystalline Ca3−2xNa2xCo4−xWxO9 (0 ≤ x ≤ 0.075) samples have been investigated.

Cited by 25 publications

References 59 publications

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

Thermoelectric Oxide Ceramics Outperforming Single Crystals Enabled by Dopant Segregations

Grain Boundary Engineering Nanostructured SrTiO₃ for Thermoelectric Applications

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High-temperature thermoelectric properties of Na- and W-Doped Ca3Co4O9 system

Abstract: The detailed crystal structures and high temperature thermoelectric properties of polycrystalline Ca3−2xNa2xCo4−xWxO9 (0 ≤ x ≤ 0.075) samples have been investigated.

Cited by 25 publications

References 59 publications

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

Effects of calcination temperature and time on the Ca3Co4O9 purity when synthesized using starch-assisted sol-gel combustion method

Thermoelectric Oxide Ceramics Outperforming Single Crystals Enabled by Dopant Segregations

Grain Boundary Engineering Nanostructured SrTiO3 for Thermoelectric Applications

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High-temperature thermoelectric properties of Na- and W-Doped Ca₃Co₄O₉ system

Grain Boundary Engineering Nanostructured SrTiO₃ for Thermoelectric Applications