Abstract
In this work, a series of Bi2Te3/X mol% MoS2 (X = 0, 25, 50, 75) bulk nanocomposites were prepared by hydrothermal reaction followed by reactive spark plasma sintering (SPS). X-ray diffraction analysis (XRD) indicates that the native nanopowders, comprising of Bi2Te3/MoS2 heterostructure, are highly reactive during the electric field-assisted sintering by SPS. The nano-sized MoS2 particles react with the Bi2Te3 plates matrix forming a mixed-anion compound, Bi2Te2S, at the interface between the nanoplates. The transport properties characterizations revealed a significant influence of the nanocomposite structure formation on the native electrical conductivity, Seebeck coefficient, and thermal conductivity of the initial Bi2Te3 matrix. As a result, enhanced ZT values have been obtained in Bi2Te3/25 mol% MoS2 over the temperature range of 300–475 K induced mainly by a significant increase in the electrical conductivity.
Highlights
Thermoelectric (TE) materials can convert heat to electricity or vice versa and the efficiency of the conversion is characterized by the dimensionless figure of merit ZT, ZT = S2 σT/κ, wherein the Seebeck coefficient (S), the electrical conductivity (σ), and the thermal conductivity (κ, including electronic component κ e, lattice component κl, and bipolar component κ b ) are three interdependent properties which depend on the absolute temperature (T) [1,2,3]
The diffraction peaks of the pristine sample X = 0 are in good agreement with the standard data for Bi2 Te3 (JCPDS no. 89-2009) and the phase purity is confirmed through the Rietveld refinement (Figure S2a and Table S1), which highlight low-reliability factors attesting to the non-degradation of the native powder during the sintering process at the select temperature (T = 623 K)
Despite the low sintering temperature, the presence of MoS2 nanoflake on the Bi2 Te3 matrix induces the formation of the Bi2 Te2 S-tetradymite phases as visible in the X = 25 and 50 powder X-ray diffraction (PXRD) patterns (Figure 1) and further confirmed by pattern matching (Figure S2b,c), which suggests a reaction/degradation occurred during the sintering process
Summary
Thermoelectric (TE) materials can convert heat to electricity or vice versa and the efficiency of the conversion is characterized by the dimensionless figure of merit ZT, ZT = S2 σT/κ, wherein the Seebeck coefficient (S), the electrical conductivity (σ), and the thermal conductivity (κ, including electronic component κ e , lattice component κl , and bipolar component κ b ) are three interdependent properties which depend on the absolute temperature (T) [1,2,3]. As the most popular candidate for TE power generation and refrigeration [19], quintuple-layered Bi2 Te3 is known as a topological insulator (TI), with an insulating bulk and metallic surface states protected by time-reversal symmetry [27,28], meaning charge carriers are not backscattered by nonmagnetic impurities and defects
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