Unveiling the synthesis mechanisms of (Bi,Sb,Sn)–Te and observation of the n-type to p-type semiconducting transition in Sb–Bi2Te3 nanostructured chalcogenides derived via an aqueous-based reflux method

Abstract

A systematic study of a surfactant-assisted, aqueous-based, low-temperature chemical method for the synthesis of (Bi,Sb,Sn)–Te nanostructures was carried out. A detailed understanding of the chemistry involved in the reaction mechanism and decomposition of ethylenediaminetetraacetic acid was proposed for different precursors of Bi, Sb and Sn, and the possibilities for the aqueous-based, low-temperature synthesis of phase pure Bi₂Te₃, SnTe, and Sb₂Te₃ was demonstrated. The reaction mechanism revealed that the aqueous-based reflux reaction is suitable for the synthesis of Bi₂Te₃, unsuitable for the synthesis of SnTe, and suitable for the partial formation of Sb₂Te₃. Hot-pressed Sb-doped Bi₂Te₃ samples exhibited an n- to p-type semiconducting transition with variations in temperature and Sb dopant concentration. A significant improvement in Seebeck coefficient and power factor values of 215.12 μV K⁻¹ and 7.1 μW m⁻¹ K⁻², respectively, was observed at 465 K for the 5% Sb-doped Bi₂Te₃ nanostructures. This work focuses primarily on the reaction mechanism of Bi-, Sb- and Sn-based tellurides in an aqueous medium, providing further possibilities in the field of chalcogenide nanostructures for thermoelectric applications.