Abstract
We report the synthesis and thermoelectric transport properties of As-doped layered pnictogen oxyselenides NdO0.8F0.2Sb1−xAsxSe2 (x ≤ 0.6), which are predicted to show high-performance thermoelectric properties based on first-principles calculation. The crystal structure of these compounds belongs to the tetragonal P4/nmm space group (No. 129) at room temperature. The lattice parameter c decreases with increasing x, while a remains almost unchanged among the samples. Despite isovalent substitution of As for Sb, electrical resistivity significantly rises with increasing x. Very low thermal conductivity of less than 0.8 Wm−1K−1 is observed at temperatures between 300 and 673 K for all the examined samples. For As-doped samples, the thermal conductivity further decreases above 600 K. Temperature-dependent synchrotron X-ray diffraction indicates that an anomaly also occurs in the c-axis length at around 600 K, which may relate to the thermal transport properties.
Highlights
A thermoelectric device is a solid-state device that can directly convert heat to electricity or vice versa without any gas or liquid working fluid [1,2,3,4,5]
A promising approach to developing novel thermoelectric materials is by utilizing the first-principles calculation of transport properties under some assumptions, such as a constant relaxation time [6,7,8,9,10,11,12,13]
We have reported the synthesis and transport properties of RE(O,F)SbSe2 for RE = La, Ce, and Nd [30,31]
Summary
A thermoelectric device is a solid-state device that can directly convert heat to electricity or vice versa without any gas or liquid working fluid [1,2,3,4,5]. The efficiency of the thermoelectric device is primarily governed by the material’s dimensionless figure of merit, ZT = S2 Tρ−1 κ−1 , where T is the absolute temperature, S is the Seebeck coefficient, ρ is the electrical resistivity, and κ is the thermal conductivity. Because these transport properties strongly correlate with each other, it is not easy to achieve high-ZT thermoelectric materials. Several candidate materials have been theoretically predicted to show high thermoelectric performance, and some have been experimentally investigated. The verification of these theoretical predictions is insufficient because some of the promising materials cannot be obtained in a thermodynamically stable phase
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