Phase analysis, thermal and thermoelectric properties of nanocrystalline Na0.15Cu1.85S, alloys Na0.17Cu1.80S, Na0.20Cu1.77S
Abstract
Synthesis, X-ray phase analysis, electron microscopy and investigations of the thermoelectric and thermal properties of nanocrystalline copper sulfide alloys contained sodium are presented. At room temperature, the alloys are a mixture of three phases of copper sulfide - the monoclinic phase of Na2Cu4S3 , the hexagonal phase of Cu2S and the cubic phase of Cu9S5 (digenite). The predominant phase is Na2Cu4S3 (with content from 57 to 85 volume %). The particle sizes in the compacted samples lie in the range from 20 to 400 nm. For all samples DSC studies revealed a first-order phase transition in the (370-380) K region with enthalpies from 5234 to 11720 J/kgK. The heat capacity varies within the range (0.15-0.48) J/(gK). The electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the temperature range from 290 to 590 K. A very low thermal conductivity of the samples was observed in the interval of (0.1-0.6) Wm -1 K -1 . The Seebeck coefficient has a value higher than 0.2 mV/K for Na0.15Cu1.85S composition, but a low electrical conductivity about 10 S/cm limits the maximum dimensionless thermoelectric efficiency ZT of the material at 0.3 in the temperature range 290-590 K.
About the Authors
M. Kh. BalapanovRussian Federation
M. M. Kubenova
Kazakhstan
K. A. Kuterbekov
Kazakhstan
A. .. Kozlovskiy
Kazakhstan
S. N. Nurakov
Kazakhstan
R. Kh. Ishembetov
Russian Federation
R. A. Yakshibaev
Russian Federation
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Review
For citations:
Balapanov M.K., Kubenova M.M., Kuterbekov K.A., Kozlovskiy A..., Nurakov S.N., Ishembetov R.K., Yakshibaev R.A. Phase analysis, thermal and thermoelectric properties of nanocrystalline Na0.15Cu1.85S, alloys Na0.17Cu1.80S, Na0.20Cu1.77S. Eurasian Journal of Physics and Functional Materials. 2018;2(3):231-241. https://doi.org/10.29317/ejpfm.2018020304