Tailoring the phase transition temperature to achieve high-performance cubic GeTe-based thermoelectrics

Suwardi, Ady; Cao, Jin; Hu, Lei; Wei, Fengxia; Wu, Jing; Zhao, Yunshan; Lim, Su Hui; Yang, Lan; Tan, Xian Yi; Chien, Sheau Wei; Yin, Yan; Zhou, Wu‐Xing; Nancy, Wong Lai Mun; Wang, Xizu; Lim, Suo Hon; Ni, Xiping; Li, Dengfeng; Yan, Qingyu; Zheng, Yun; Zhang, Gang; Xu, Jianwei

doi:10.1039/d0ta06013e

Cited by 76 publications

(38 citation statements)

References 70 publications

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“… (a) zT as a function of temperature for all samples. (b) Average zT between 300–800 K in this work in comparison with those reported in literatures [72–74] …”

Section: Resultssupporting

confidence: 66%

“…Besides electronic properties, a unique feature of GeTe lies in its rhombohedral structure at room temperature, which undergoes phase transition to cubic at 700 K. While the rhombohedral distortion favours low thermal conductivity, it also presents problem due to the anomaly in thermal expansion during phase transition. Therefore, it is desirable suppress the phase transition and achieve all‐cubic phase in GeTe [72–74] . In this work, we seek to achieve pure cubic GeTe with high thermoelectric performance.…”

Section: Introductionmentioning

confidence: 99%

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Realizing zT Values of 2.0 in Cubic GeTe

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Over the past two years, GeTe has quickly cemented its place as the best performing thermoelectric material at a medium temperature range. The key factors behind the extraordinary performance lie in its favourable electronic and thermal properties, which arise from its unique crystal structure. The slight rhombohedral distortion at temperatures below 700 K results in lower lattice thermal conductivity while maintaining high electronic properties via high level of band‐convergence. In addition, while GeTe has a cubic structure above 700 K, the local atomic disorder persists, which maintains its low thermal conductivity. To date, the understanding of the temperature‐dependent thermoelectric properties of cubic GeTe at room temperature and above is very limited. This is due to the difficulties in stabilizing cubic GeTe at low temperatures. In this work, we leverage on low level of Ti doping to stabilize cubic‐phase GeTe at room temperature and elucidate its temperature‐dependent electronic and thermal properties. Further doping with In, Cu, Sb, and Pb results in zT as high as 2 at 773 K, and high average zT of 1.4 between 300 and 800 K.

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“… (a) zT as a function of temperature for all samples. (b) Average zT between 300–800 K in this work in comparison with those reported in literatures [72–74] …”

Section: Resultssupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Realizing zT Values of 2.0 in Cubic GeTe

et al. 2021

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“…The hot vacuum pressing procedure increases the sample density. The sample treatment in vacuum at 650 °C results the optimum Seebeck coefficient value (~200 uV/K), typical for SnSe- and GeTe-based thermoelectric materials [ 28 , 29 ]. Thus, the sample treatment procedure could be used to optimize the Seebeck coefficient value both the cationic substitution of CuCrS 2 -matrix [ 11 ].…”

Section: Resultsmentioning

confidence: 99%

“…As a result, the MCrX 2 conductivity and the order-disorder phase transition (ODT) are increased. Note that CuCrS 2 structure does not significantly changes before and after ODT phase transition [ 27 ], in contrast the traditional to SnSe- and GeTe-based thermoelectric materials [ 28 , 29 ], where phase transition is accompanied by the spatial group changes. Hence, the similarity of CuCrS 2 and Se/Te-based systems is that both demonstrate phase transitions.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Order-Disorder Transition on the Electronic Structure and Physical Properties of Layered CuCrS2

et al. 2021

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The work reports a comprehensive study of the Seebeck coefficient, electrical resistivity and heat capacity of CuCrS2 in a wide temperature range of 100–740 K. It was shown that the value of the Seebeck coefficient is significantly affected by the sample treatment procedure. The order-to-disorder (ODT) phase transition was found to cause a metal-insulator transition (MIT). It was established that the ODT diminishes the Seebeck coefficient at high temperatures (T > 700 K). The DFT calculations of the CuCrS2 electronic structure showed that the localization of copper atoms in octahedral sites makes the band gap vanish due to the MIT. The decrease of CuCrS2 electrical resistivity in the ODT temperature region corresponds to the MIT.

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“…However, the introduced dopants can deteriorate the charge carrier mobility, thus hindering the magnitude of the optimal power factor [9,10]. A popular and effective strategy for enhancing the PF is via the electronic band-engineering [11][12][13][14][15][16]. In the electronic band-engineering, either the band-convergence or the effective mass manipulation can be explored to increase the S or σ, respectively [13,17,18].…”

Section: Introductionmentioning

confidence: 99%

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

Zhu

Wang

et al. 2021

Nano-Micro Lett.

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The recent advancements in thermoelectric materials are largely credited to two factors, namely established physical theories and advanced materials engineering methods. The developments in the physical theories have come a long way from the “phonon glass electron crystal” paradigm to the more recent band convergence and nanostructuring, which consequently results in drastic improvement in the thermoelectric figure of merit value. On the other hand, the progresses in materials fabrication methods and processing technologies have enabled the discovery of new physical mechanisms, hence further facilitating the emergence of high-performance thermoelectric materials. In recent years, many comprehensive review articles are focused on various aspects of thermoelectrics ranging from thermoelectric materials, physical mechanisms and materials process techniques in particular with emphasis on solid state reactions. While bottom-up approaches to obtain thermoelectric materials have widely been employed in thermoelectrics, comprehensive reviews on summarizing such methods are still rare. In this review, we will outline a variety of bottom-up strategies for preparing high-performance thermoelectric materials. In addition, state-of-art, challenges and future opportunities in this domain will be commented.

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Tailoring the phase transition temperature to achieve high-performance cubic GeTe-based thermoelectrics

Abstract: GeTe is highly sought-after due to its versatility as high-performance thermoelectrics, phase change materials, as well as ferroelectric Rashba semiconductor. Compared to most thermoelectric materials, it has an additional degree...

Cited by 76 publications

References 70 publications

Realizing zT Values of 2.0 in Cubic GeTe

Realizing zT Values of 2.0 in Cubic GeTe

Effect of the Order-Disorder Transition on the Electronic Structure and Physical Properties of Layered CuCrS2

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

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