Effect of Carbon Nanotubes on Thermoelectric Properties in Zn0.98Al0.02O

Dreßler, Christian; Löhnert, Romy; González‐Julián, Jesús; Guillon, Olivier; Töpfer, J.; Teichert, S.

doi:10.1007/s11664-015-4070-4

Cited by 15 publications

(7 citation statements)

References 36 publications

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“…[3][4][5] To achieve high conversion efficiency, the TE material must have a high power factor (S 2 σ), as well as low total thermal conductivity. [6][7][8] However, due to the intercorrelation of the transport parameters, optimizing the TE performance is relatively complex. Because the electrical properties involving S, σ and κ e are strongly coupled, [9] improving one of these three parameters will result in compensation for other parameters that impede progress toward improving TE performance.…”

Section: Introductionmentioning

confidence: 99%

Effect of Powder ALD Interface Modification on the Thermoelectric Performance of Bismuth

Bahrami

Zhang

et al. 2021

Adv Materials Technologies

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In thermoelectric materials, phase boundaries are crucial for carrier/phonon transport. Manipulation of carrier and phonon scatterings by introducing continuous interface modification has been shown to improve thermoelectric performance. In this paper, a strategy of interface modification based on powder atomic layer deposition (PALD) is introduced to accurately control and modify the phase boundary of pure bismuth. Ultrathin layers of Al2O3, TiO2, and ZnO are deposited on Bi powder by typically 1–20 cycles. All of the oxide layers significantly alter the microstructure and suppressed grain growth. These hierarchical interface modifications aid in the formation of an energy barrier by the oxide layer, resulting in a substantial increase in the Seebeck coefficient that is superior to that of most pure polycrystalline metals. Conversely, taking advantage of the strong electron and phonon scattering, an exceptionally large decrease in thermal conductivity is obtained. A maximum figure of merit, zT, of 0.15 at 393 K and an average zT of 0.14 at 300–453 K were achieved in 5 cycles of Al2O3‐coated Bi. The ALD‐based approach, as a practical interfacial modification technique, can be easily applied to other thermoelectric materials, which can contribute to the development of high‐performance thermoelectric materials of great significance.

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Section: Introductionmentioning

confidence: 99%

Effect of Powder ALD Interface Modification on the Thermoelectric Performance of Bismuth

Bahrami

Zhang

et al. 2021

Adv Materials Technologies

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“…On the other hand, a good conductive network is established in the matrix owing to the homogeneous dispersion of in-situ grown CNTs, which facilitates the transport of electrons. In contrast, for the sample with commercial CNTs by ultrasonic technology, the electrical conductivity is much lower, mainly due to the agglomeration of CNTs, which prevents the excellent conductivity of CNTs from being effectively utilized [34].…”

Section: Resultsmentioning

confidence: 99%

“…They have been thus widely used as a reinforcement in many fields [31][32][33]. For example, Dreßler et al [34] mixed AZO powders and multi-walled CNTs by ultrasonic dispersion and mechanical milling, and then sintered the mixture by the spark plasma sintering (SPS). The results indicated that the thermal conductivity decreased from 31.2 to 26 W•m −1 •K −1 after the incorporation of multi-walled CNTs.…”

Section: Introductionmentioning

confidence: 99%

In-situ growth of carbon nanotubes on ZnO to enhance thermoelectric and mechanical properties

et al. 2022

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As a high-temperature thermoelectric (TE) material, ZnO offers advantages of non-toxicity, chemical stability, and oxidation resistance, and shows considerable promise as a true ready-to-use module under air conditions. However, poor electrical conductivity and high thermal conductivity severely hinder its application. Carbon nanotubes (CNTs) are often used as a reinforcing phase in composites, but it is difficult to achieve uniform dispersion of CNTs due to van der Waals forces. Herein, we developed an effective in-situ growth strategy of homogeneous CNTs on ZnO nanoparticles by exploiting the chemical vapor deposition (CVD) technology, in order to improve their electrical conductivity and mechanical properties, as well as reducing the thermal conductivity. Meanwhile, magnetic nickel (Ni) nanoparticles are introduced as catalysts for promoting the formation of CNTs, which can also enhance the electrical and thermal transportation of ZnO matrices. Notably, the electrical conductivity of ZnO is significantly boosted from 26 to 79 S·cm−1 due to the formation of dense and uniform conductive CNT networks. The lattice thermal conductivity (κL) is obviously declined by the intensification of phonon scattering, resulting from the abundant grain boundaries and interfaces in ZnO-CNT composites. Importantly, the maximum dimensionless figure of merit (zT) of 0.04 at 800 K is obtained in 2.0% Ni-CNTs/ZnO, which is three times larger than that of CNTs/ZnO prepared by traditional ultrasonic method. In addition, the mechanical properties of composites including Vickers hardness (HV) and fracture toughness (KIC) are also reinforced. This work provides a valuable reference for dispersing nano-phases in TE materials to enhance both TE and mechanical properties.

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“…It has been stated that the energy barrier should be adjusted to 0.2 eV in order to obtain optimal energy filtering effect. [ 175 ] Some research found that increasing the CNT concentration increased electrical conductivity, [ 172,174,176,177 ] whereas others found the reverse. [ 178–181 ] The changing CNT content might explain this discrepancy.…”

Section: Discontinuous Interface Modificationmentioning

confidence: 99%

Current State‐of‐the‐Art in the Interface/Surface Modification of Thermoelectric Materials

Lehmann

Bahrami

et al. 2021

Advanced Energy Materials

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Thermoelectric (TE) materials are prominent candidates for energy converting applications due to their excellent performance and reliability. Extensive efforts for improving their efficiency in single‐/multi‐phase composites comprising nano/micro‐scale second phases are being made. The artificial decoration of second phases into the thermoelectric matrix in multi‐phase composites, which is distinguished from the second‐phase precipitation occurring during the thermally equilibrated synthesis of TE materials, can effectively enhance their performance. Theoretically, the interfacial manipulation of phase boundaries can be extended to a wide range of materials. High interface densities decrease thermal conductivity when nano/micro‐scale grain boundaries are obtained and certain electronic structure modifications may increase the power factor of TE materials. Based on the distribution of second phases on the interface boundaries, the strategies can be divided into discontinuous and continuous interfacial modifications. The discontinuous interfacial modifications section in this review discusses five parts chosen according to their dispersion forms, including metals, oxides, semiconductors, carbonic compounds, and MXenes. Alternatively, gas‐ and solution‐phase process techniques are adopted for realizing continuous surface changes, like the core–shell structure. This review offers a detailed analysis of the current state‐of‐the‐art in the field, while identifying possibilities and obstacles for improving the performance of TE materials.

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Effect of Carbon Nanotubes on Thermoelectric Properties in Zn0.98Al0.02O

Cited by 15 publications

References 36 publications

Effect of Powder ALD Interface Modification on the Thermoelectric Performance of Bismuth

Effect of Powder ALD Interface Modification on the Thermoelectric Performance of Bismuth

In-situ growth of carbon nanotubes on ZnO to enhance thermoelectric and mechanical properties

Current State‐of‐the‐Art in the Interface/Surface Modification of Thermoelectric Materials

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