Research on a new thermoelectric material obtained by doping of n-HfNiSn with Nb atoms

Abstract

The structural, kinetic, energetic, and magnetic properties of the new thermoelectric material Hf_1-xNb_xNiSn, obtained by doping the n-HfNiSn semiconductor with Nb atoms introduced into the structure by substituting Hf atoms in the crystallographic position 4a, have been investigated. It has been established that at concentrations of x=0.02 inclusive, there is a solid solution of Hf_1-xNb_xNiSn substitution of Hf atoms (5d²6s²) for Nb atoms (4d⁴5s¹). In this case, defects of donor nature are generated in the Hf_1-xNb_xNiSn structure (Nb contains more d-electrons than the Hf atom), and impurity donor states ε_D appear in the band gap ε_g. At concentrations of 0.02<х≤0.05, substitution probably occurs by displacing Ni atoms from position 4a, which in the original HfNiSn compound was occupied by a statistical mixture of Hf and Ni atoms. In this case, defects of an acceptor nature are generated in the Hf_1-xNb_xNiSn structure (Nb contains fewer d-electrons than the Ni atom), and impurity acceptor states ε_А appear in the band gap ε_g. The ratio of donor and acceptor states determines the type of conductivity of Hf_1-xNb_xNiSn. It is shown that the semiconductive solid solution Hf_1-xNb_xNiSn is highly efficient in converting thermal energy into electrical energy.