Pre-oxidation effects on properties of bismuth telluride thermoelectric composites compacted by spark plasma sintering

Abstract

Research on harvesting alternative energy sources is of interest to meet human demands for energy while reducing environmental pollution caused by the extensive use of fossil fuels. Thermoelectric materials are a promising technology for converting heat into electricity. Among thermoelectric materials, the binary bismuth telluride system (Bi-Te) is widely used. To produce high-quality BiTe systems with low materials consumption, spark plasma sintering (SPS) is commonly applied. Because SPS is a fast low-temperature process, controlling the ratio and crystallization of BiTe is critical for effective energy conversion. Here, we investigated the quality of BiTe systems formed by SPS compaction of raw powders with an in-depth examination of the oxidation effects on their thermoelectric performance. With increasing measurement temperature (300→420 K), the mechanically mixed sample and a commercial Bi 2 Te 3 alloy (sintered at 533 K) showed differences in Seebeck coefficients (0.245→0.267 and 0.223→0.246 mVK −1 , respectively). The alloy sample showed a decreased figure of merit (0.863→0.331) while that of the mechanically mixed sample (0.543→1.671) increased with temperature. This was related to the degree of oxygen impurity in each BiTe process based on XPS analysis. This study proposes that the integration of oxygen species to BiTe can be considered to maximize the thermoelectric efficiency at the specified temperature.

Dimethylammonium iodide stabilized bismuth halide perovskite photocatalyst for hydrogen evolution

“…S8 in the ESM). The additional peaks located at 155.6 and 160.9 eV (Δ = 5.3 eV) can be assigned to metallic bismuth [60], originating from partial reduction of trivalent bismuth after exposure to X-ray. Similar behavior was often observed in other metal halide materials [61][62][63].…”

Facile Fabrication of Flexible and High‐Performing Thermoelectrics by Direct Laser Printing on Plastic Foil

“…This is illustrated in Figure S6, Supporting Information, by the presence of metal‐bonded oxygen species in the O1s peak (530 eV), and the oxidized Bi component in Bi4f (159 eV), as well as oxidized Te species in the Te3d peak (576–577 eV). [ 45–48 ] The formation of this oxide was also detected by XRD (Figure S9, Supporting Information). The evolution of the surface oxidation throughout the fabrication process is represented in Figure S12, Supporting Information.…”

Enhanced Thermoelectric Performance in n-Type Bi2O2Se by an Exquisite Grain Boundary Engineering Approach

“…The main peak lies at ∼529.4 eV, which might be related to lattice oxygen from metal-oxide bonds in the sample. Two other peaks located at 530.7 and 532.2 eV might be associated with dangling bonds (O – ; O 2 – ) generated from surficial oxygen vacancies of Bi 2 O 2 Se and surface-absorbed oxygen severally . In Figure (b3), the Se 3d orbitals of displayed samples contain two characteristic peaks.…”