Abstract
Structural, electrokinetic and energy state characteristics of the Zr1-xVxNiSn semiconductive solid solution (х=0–0.10) were investigated in the temperature interval 80–400 К. It was shown that doping of the ZrNiSn compound by V atoms (rV=0.134 nm) due to substitution of Zr (rZr=0.160 nm) results in increase of lattice parameter а(х) of Zr1-xVxNiSn indicating unforecast structural change. Based on analysis of the motion rate of the Fermi level ΔεF/Δх for Zr1-xVxNiSn in direction of the conduction band it was concluded about simultaneous generation of the structural defects of the donor and acceptor nature (donor-acceptor pairs) by unknown mechanism and creation of the corresponding energy levels in the band gap of the semiconductor.
Highlights
The importance of the study of electroconductivity mechanism of the thermoelectric materials based on the n-ZrNiSn, n-HfNiSn and n-TiNiSn intermetallic semiconductors is due to the fact that thermoelectric materials based on the above-mentioned semiconductors have high efficiency of conversion of thermal energy into electric, and optimization of their characteristics is carried out by appropriate doping [1, 2]
An analysis of the research results of the semiconductive solid solutions based on half-Heusler phases showed the difference between experimental measurements, for example, electrical resistivity and thermopower coefficient values and modeling of these characteristics by calculation of electronic structure
The formulas of the solid solutions can be written as ТіNiSn1-x-yGax and ZrNiSn1-x-yGax, where y is the concentration of vacancies in 4b position of Sn atoms
Summary
The importance of the study of electroconductivity mechanism of the thermoelectric materials based on the n-ZrNiSn, n-HfNiSn and n-TiNiSn intermetallic semiconductors is due to the fact that thermoelectric materials based on the above-mentioned semiconductors have high efficiency of conversion of thermal energy into electric, and optimization of their characteristics is carried out by appropriate doping [1, 2]. The concentration of the defects increases with Ga content, and semiconductors become heavily doped and highly compensated (HDHCS) [9] At first sight, such unexpected result is logical, since the stability of structure and the principle of electroneutrality for the crystals of TiNiSn1-хGax and ZrNiSn1-хGax in the case of significant number of acceptors (NAGa ≈ 3·1021 см-3) are provided by the generation of structural defects of donor nature, the effective charge of which is the opposite. In this case, the formulas of the solid solutions can be written as ТіNiSn1-x-yGax and ZrNiSn1-x-yGax, where y is the concentration of vacancies in 4b position of Sn atoms. It worth to note that atomic radii of Rh and V are the same, but the way of their introduction in the structure of the compound is different
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