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High-performance and Low Thermal Conductivity in Nano-layered Cu2Se prepared by NaCl-flux method

Abstract

In this study, nano-layered Cu2Se high-performance material is successfully grown using NaCl-flux method based on the stoichiometric ratios of Cu2Se(NaCl)x (x = 1.5, 2, 2.5, 3, and 3.5). X-ray diffraction results show that samples possess an -phase structure for 1.5 x 2.5, whereas samples consist of a mixture of - and -phase structures for x 3. Electron probe microanalysis results present that almost no Na or Cl atoms were found in all samples. Meanwhile, the actual composition is close to the nominal composition of Cu2Se when 1.5 x 2.5, whereas it deviates from the nominal composition when x 3. The valence values of Cu and Se atoms are +1 and −2 in the sample, respectively. Transmission electron microscopy results prove that the crystals prepared using the NaCl-flux method have a good quality. The field emission scanning electron microscopy image shows that the samples prepared using the NaCl-flux method have a stacking nano-layered structure with an average thickness of approximately 110 nm. These thin lamellar crystals have several grain boundaries, which can effectively scatter the phonon and thus result in ultra-low lattice thermal conductivity. Cu2Se(NaCl)2.5 exhibits the best thermoelectric performance among all samples because it has the lowestthermal conductivity. The maximum ZT value reaches 1.42 at 700 K, which is much higher than those prepared using fast melt-quenching method (~0.88 at 700 K), spark plasma sintering (~0.8 at 700 K) and high-temperature and high-pressure synthesis (~1.13 at 700 K).

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Publication details

The article was received on 10 Aug 2019, accepted on 08 Oct 2019 and first published on 10 Oct 2019


Article type: Paper
DOI: 10.1039/C9CE01258C
CrystEngComm, 2019, Accepted Manuscript

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    High-performance and Low Thermal Conductivity in Nano-layered Cu2Se prepared by NaCl-flux method

    W. Liu, L. Shen, X. Shai, L. Sun, J. Lu, J. Cheng, W. Ge and S. Deng, CrystEngComm, 2019, Accepted Manuscript , DOI: 10.1039/C9CE01258C

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