Electrical transport properties and electronic structure of RNiSn compounds (R = Y, Gd, Tb, Dy, and Lu)

Abstract

A series of RNiSn compounds, where R = Y, Gd, Tb, Dy, and Lu, with the TiNiSi structure type (space group Pnma) was synthesized and the electrical transport properties were investigated by means of electrical resistivity and Seebeck coefficient measurements in the temperature range 80-380 K. All of the investigated compounds exhibit metallic-like conductivity. Electronic structure calculations based on the Full Potential Linearized Augmented Plane Wave (FLAPW) method were carried out to obtain the density of states (DOS) for the investigated compounds, from which the electrical properties were explained.

Effect of secondary LuNiSn phase on thermoelectric properties of half-Heusler alloy LuNiSb

“…The latter two samples show metallic behavior. For LuNiSn, the  value at 380 K is of the order of 1 m, in reasonable agreement with the literature data [29]. For the composite sample, the  value is twice larger, which can be attributed to crystallographic disorder and secondary phase inclusions.…”

“…The S value near room temperature equals 3.6 µV/K, i.e. significantly differs from that reported before (S  -7.2 µV/K [29]). In the case of LuNiSb, the Seebeck coefficient is positive and S(T) forms a maximum near 600 or 650 K, depending on the sample.…”

“…The index x refers to the TiNiSi-type phase weight fraction determined from XRD by the Rietveld method. The lattice parameters derived for LuNiSn are in good agreement with the literature data [28,29]. For the two prepared alloys of LuNiSb, the lattice parameter aHH is slightly smaller than the values reported in the literature [20,21], and it is somewhat sample-dependent.…”

“…The metallic constituent selected, i.e., LuNiSn, crystallizes in the orthorhombic TiNiSi-type structure (space group Pnma, No. 62) [28,29]. Alike LuNiSb it is a Pauli paramagnet, yet its electrical conductance has a metallic character, and its thermopower is small and negative (S = 7.2 V/K) at room temperature [29].…”

“…62) [28,29]. Alike LuNiSb it is a Pauli paramagnet, yet its electrical conductance has a metallic character, and its thermopower is small and negative (S = 7.2 V/K) at room temperature [29]. Our selection of LuNiSn being an ingredient in the LuNiSb-based composite was motivated by the fact of (i) its metallic transport properties, (ii) similar chemical composition, (iii) different crystal structure with distinctly different lattice parameters.…”