Extremely Fast and Cheap Densification of Cu2S by Induction Melting Method.

Paweł Nieroda,Andrzej Koleżyński,Paweł Rutkowski,Krzysztof Ziewiec,Juliusz Leszczyński

doi:10.3390/ma14237311

Paweł Nieroda, Andrzej Koleżyński + Show 3 more

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https://doi.org/10.3390/ma14237311

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Abstract

The aim of this work was to obtain dense Cu2S superionic thermoelectric materials, homogeneous in terms of phase and chemical composition, using a very fast and cheap induction-melting technique. The chemical composition was investigated via scanning electron microscopy (SEM) combined with an energy-dispersive spectroscopy (EDS) method, and the phase composition was established by X-ray diffraction (XRD). The thermoelectric figure of merit ZT was determined on the basis of thermoelectric transport properties, i.e., Seebeck coefficient, electrical and thermal conductivity in the temperature range of 300–923 K. The obtained values of the ZT parameter are comparable with those obtained using the induction hot pressing (IHP) technique and about 30–45% higher in the temperature range of 773–923 K in comparison with Cu2S samples densified with the spark plasma sintering (SPS) technique.

Highlights

Cu2 S is an environmentally friendly and low-cost superionic thermoelectric material that has been intensively studied in recent years as a potential material for thermoelectric generator applications [1,2,3,4]
The energy conversion efficiency of such thermoelectric generators depends on the temperature difference between the junctions of the thermoelectric materials and the properties of materials expressed by the value of the thermoelectric figure of merit, ZT = α2 σλ−1 T [5,6], (α—Seebeck coefficient, σ—electrical conductivity, λ—thermal conductivity)
The induction melting (IM) method offers very short compaction times, and the remelting time is so brief that the mixing and segregation processes have virtually no time to take place

Summary

Introduction

Cu2 S is an environmentally friendly and low-cost superionic thermoelectric material that has been intensively studied in recent years as a potential material for thermoelectric generator applications [1,2,3,4]. The remarkable thermoelectric properties of Cu2 S, both undoped and doped with e.g., Se [2], in particular for the high-temperature cubic phase α-Cu2 S (T > 708 K) [7] are closely related to the migration of copper ions. The migration of ions in the Cu2 S crystal structure, on the one hand, has a positive effect on the thermoelectric properties, i.e., a decrease in thermal conductivity and an increase in the electrical conductivity of the material, but on the other hand causes a lack of stability of Cu2 S under electric current. This may result in a deficiency of copper atoms in the Cu2 S structure, which affects the transport properties of the material [10]

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