Features of Mechanisms of Electrical Conductivity in Semiconductive Solid Solution Lu1 – xScxNiSb

Abstract

A comprehensive study of the crystal and electronic structures, thermodynamic, electrokinetic, energy, and magnetic properties of the semiconductive solid solution Lu1-xScxNiSb, x = 0 – 0.10, revealed the possibility of doping Sc atoms of different crystallographic sites depending on their concentration. This leads to the generation of structural defects of donor and/or acceptor nature and the appearance of the corresponding energy levels (bands) in the band gap єg. The ratio of ionized donors and acceptors (degree of compensation) determines the position of the Fermi level єF in Lu1-xScxNiSb. The dependence of the rate of generation of energy levels and the position of the Fermi level єF on the impurity concentration Sc, which determines the mechanism of electrical conductivity of Lu1-xScxNiSb, is established. The investigated Lu1-xScxNiSb solid solution is a promising thermoelectric material.

Peculiarities of structural, electrokinetic, energetic, and magnetic properties semiconductive solid solution Lu1-xVxNiSb

“…1, in the concentration range x=0-0.03, the values of а(х) for Lu1-xVxNiSb increase, pass through a maximum, and rapidly decrease at x>0.03. By the way, we observed a similar behavior of the unit cell parameter a(x) in the Lu1-xZrxNiSb solid solution [10,11] (Fig. 1, inset).…”

“…In this context, it seems interesting to study when V atoms (3d 3 4s 2 ) will be introduced into the structure of the half-Heusler LuNiSb phase by replacing Lu atoms in the 4a position. A priori, as in the case of Lu1-xZrxNiSb [10,11], we expected the generation of only donor defects in the Lu1-xVxNiSb structure, х=0-0.10, since the V atom has a higher number of d-electrons than Lu. On the other hand, the atomic radius of V (rV=0.134 nm) is much smaller than that of Lu (rLu=0.173 nm) and close to the atomic radius of Ni (rNi=0.125 nm).…”

“…The study of the structural, electrokinetic, energetic, and magnetic properties of semiconductive substitutional solid solutions based on half-Heusler phases, in particular, based on RNiSb (R -Y, Gd -Lu) compounds [4][5][6][7][8][9][10][11], allows us to understand the nature of processes of charges transport. After all, the optimization of the electrokinetic characteristics of thermoelectric materials to increase the efficiency of the conversion of thermal energy into electrical energy is carried out by appropriate doping of half-Heusler phases with donor and/or acceptor impurities [12].…”

“…It was shown in Refs. [1,[4][5][6][7][8][9][10][11] that the crystal structure of half-Heusler RNiSb phases is defective. Vacancies are present in crystallographic positions 4a of R atoms and 4c of Ni atoms, which are structural defects of an acceptor nature.…”

“…In the case of introducing into the structure of the half-Heusler LuNiSb phase, the lowest concentration of Zr atoms (4d 2 5s 2 ), x = 0.01, the behavior of the electrokinetic characteristics is fundamentally different than when Sc atoms are introduced [10,11]. The metallic (nonactivation) nature of the behavior of the temperature dependences of the resistivity ρ(T,х) and the negative values of the thermopower coefficient α(Т,х) of Lu1-xZrxNiSb at all concentrations of Zr atoms indicate that the Fermi level εF crossed the percolation level of the conduction band εС.…”