Thermal and Electronic Transport Properties of the Half-Heusler Phase ScNiSb

Abstract

Thermoelectric properties of the half-Heusler phase ScNiSb (space group F 4 ¯ 3m) were studied on a polycrystalline single-phase sample obtained by arc-melting and spark-plasma-sintering techniques. Measurements of the thermopower, electrical resistivity, and thermal conductivity were performed in the wide temperature range 2–950 K. The material appeared as a p-type conductor, with a fairly large, positive Seebeck coefficient of about 240 μV K−1 near 450 K. Nevertheless, the measured electrical resistivity values were relatively high (83 μΩm at 350 K), resulting in a rather small magnitude of the power factor (less than 1 × 10−3 W m−1 K−2) in the temperature range examined. Furthermore, the thermal conductivity was high, with a local minimum of about 6 W m−1 K−1 occurring near 600 K. As a result, the dimensionless thermoelectric figure of merit showed a maximum of 0.1 at 810 K. This work suggests that ScNiSb could be a promising base compound for obtaining thermoelectric materials for energy conversion at high temperatures.

Synthesis and electrical transport properties of Er1-xScxNiSb semiconducting solid solution

“…In the present paper, the first results of experimental studies of new thermoelectric material based on an Er1-xScxNiSb semiconductor solid solution obtained by doping of ErNiSb half-Heusler phase by Sc atoms in the way of Er atoms substitution in 4a position were reported. The ScNiSb compound, which is the opposite to ErNiSb end member of solid solution Er1-xScxNiSb at x = 1, is also a semiconductor with hole-type of conduction, and its thermopower coefficient reaches maximum values α = 240 μV/K at 450 K [10]. It was stated by authors of Ref.…”

“…It was stated by authors of Ref. [10] that the vacancies, which generate structural defects of acceptor nature in 4c position and form the corresponding acceptor band, are responsible for the hole type of conduction of р-ScNiSb. Therefore, the substitution of rare earth metal Er atoms by Sc atoms, which are in the same group of the Periodic table of elements, should allow obtaining a continuous semiconductor solid solution Er1-xScxNiSb of hole-type of conduction with a smooth change of its parameters.…”

Modeling of structural and energetic parameters of р-Er1-xScxNiSb semiconductor

“…1а, curve 1). The experimental results of the previous work [8] in the concentrations range of Sc, x = 0 -0.10, and the lattice parameter value for p-ScNiSb according to the data [10] are also given for comparison with the calculated lattice parameter values a(x) in Fig. 1a atomic radius of Sc (rSc = 0.164 nm) is smaller than that in Er (rEr = 0.176 nm).…”

“…Since both ErNiSb and ScNiSb compounds crystallize in the MgAgAs structure type [10,14], to check the existence of a continuous substitutional solid solution p-Er1-xScxNiSb, the variation of the unit cell parameter a(x) was calculated within the theory of functional density DFT in the concentration range x = 0 -1.0 (Fig. 1а, curve 1).…”

“…In turn, the authors of Ref. [10] found that the ScNiSb compound, which is on the opposite side of the Tm1-xScxNiSb solid solution, x = 1.0, is also a p-type semiconductor, and the thermopower coefficient value α(T,x) is maximal at temperature Т ≈ 450 K (α =240 V/K). According to the authors [10], only vacancies in the position 4c of Ni atoms, which generate the defects of acceptor nature, are responsible for the hole type of conductivity for p-ScNiSb.…”