Enhanced thermoelectric properties of nanostructured n-type Bi₂Te₃ by suppressing Te vacancy through non-equilibrium fast reaction

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As one promising low-temperature thermoelectric material, Bi₂Te₃ suffers from high carrier concentrations beyond the optimal value contributed by excess Te vacancies. In this study, Te vacancies can be effectively suppressed in the n-type nanostructured Bi₂Te₃ via a non-equilibrium reaction induced by spark plasma sintering. The electron concentration has been greatly reduced from pristinely ~1 × 10²⁰ to ~7 × 10¹⁹ cm⁻³, generating a decent power factor of 12.84 µW cm⁻¹ K⁻² at 320 K. Meanwhile, the decreased electronic thermal conductivity due to deteriorated electrical conductivity enables a very low thermal conductivity of 0.48 W m⁻¹ K⁻¹, which ultimately secures a promising peak figure of merit zT of ~1.1 at 420 K and an outstanding average zT of ~1 from 320 to 470 K. Such a high performance is one of the cutting-edge values reported in binary n-type Bi₂Te₃ so far. Our study provides a new insight into manipulating intrinsic point defects in nanostructured Bi₂Te₃ thermoelectric materials for achieving higher zT.