Abstract
The aim of the work was to obtain copper (I) selenide Cu2Se material with excellent thermoelectric properties, synthesized using the hydrothermal method and densified by the spark plasma sintering (SPS) method. Chemical and phase composition studies were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. Measurements of thermoelectric transport properties, i.e., electrical conductivity, the Seebeck coefficient, and thermal conductivity in the temperature range from 300 to 965 K were carried out. Based on these results, the temperature dependence of the thermoelectric figure of merit ZT as a function of temperature was determined. The obtained, very high ZT parameter (ZT~1.75, T = 965 K) is one of the highest obtained so far for undoped Cu2Se.
Highlights
Cu2Se is one of the most intensively studied thermoelectric materials in recent years, suitable for the construction of thermoelectric generators that work in a medium temperature range (600–950 K) [1]
The basic parameter describing the thermoelectric properties of materials is the thermoelectric figure of merit ZT, ZT = α2σλ−1T, where α is the Seebeck coefficient, σ is the electrical conductivity, λ is the thermal conductivity, and T is the temperature
A value of the ZT parameter is directly related to the efficiency of thermoelectric devices such as thermoelectric generators and thermoelectric heat pumps, which increases with increasing ZT
Summary
Cu2Se is one of the most intensively studied thermoelectric materials in recent years, suitable for the construction of thermoelectric generators that work in a medium temperature range (600–950 K) [1]. According to PLEC, in Cu2Se having a regular calcium antifluoride crystal structure, Se atoms occupy 4a Wyckoff’s position and form an anionic framework, ensuring free movement of electron carriers through crystal lattice nodes, while very mobile copper ions (with diffusivity at 10−5 cm2s−1 T = 430 K for Cu2Se [13]) forming cationic sublattice can “jump” at short time intervals between equivalent positions (8c and 32f) in crystal lattice [10] This leads to a strong phonon scattering and results in a very low thermal conductivity in these materials (comparable to the thermal conductivity of glasses) and, increased electrical conductivity [4,10]. A very quick, one-step method for the preparation of Cu2Se using arc-melting was proposed by Butt et al [24]
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