Vacancy Manipulation by Ordered Mesoporous Induced Optimal Carrier Concentration and Low Lattice Thermal Conductivity in BixSb2−xTe3 Yielding Superior Thermoelectric Performance
For Bi x Sb 2− x Te 3 (BST) in thermoelectric field, the element ratio is easily influenced by the chemical environment, deviating from the stoichiometric ratio and giving rise to various intrinsic defects. In P-type polycrystalline BST, Sb Te and Bi Te are the primary forms of defects. Defect engineering is a crucial strategy for optimizing the electrical transport performance of Bi 2 Te 3 -based materials, but achieving synchronous improvement of thermal performance is challenging. In this study, mesoporous SiO 2 is utilized to successfully mitigate the adverse impacts of vacancy defects, resulting in an enhancement of the electrical transport performance and a pronounced reduction in thermal conductivity. Crystal and the microstructure of the continuous modulation contribute to the effective phonon–electronic decoupling. Ultimately, the peak zT of Bi 0.4 Sb 1.6 Te 3 /0.8 wt% SiO 2 (with a pore size of 4 nm) nanocomposites reaches as high as 1.5 at 348 K, and a thermoelectric conversion efficiency of 6.6% is achieved at Δ T = 222.7 K. These results present exciting possibilities for the realization of defect regulation in porous materials and hold reference significance for other material systems.
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