Abstract
The energy expediency of the existence of Er1-xScxNiSb substitutional solid solution up to the concentration x≈0.10 was established by modeling the variation of free energy ΔG(x) values (Helmholtz potential). At higher Sc concentrations, x> 0.10, there is stratification (spinoidal decomposition of phase). It is shown that in the structure of p-ErNiSb semiconductor there are vacancies in positions 4a and 4c of Er and Ni atoms, respectively, generating structural defects of acceptor nature. The number of vacancies in position 4a is twice less than in position 4c. This ratio also remains for p-Er1-xScxNiSb. Doping of p-ErNiSb semiconductor by Sc atoms by substitution of Er atoms is also accompanied by the occupation of vacancies in position 4a. In this case, Ni atoms occupy vacancies in position 4c, which can be accompanied by the process of ordering the p-Er1-xScxNiSb structure. Occupation of vacancies by Sc and Ni atoms leads to an increase of the concentration of free electrons, an enlarge of the compensation degree of semiconductor, which changes the position of the Fermi level εF and the mechanisms of electrical conductivity.
Highlights
Important components of modern research are both experimental results obtained using a variety of highly efficient equipment and theoretical studies that describe, explain experimental data, and, in most cases, serve as a basis for the predictive search for new materials and optimization of their functional characteristics.Semi-Heusler phases RNiSb (R is a rare earth metal) and solid solutions based on them with a structure of the MgAgAs type proved to be promising in the direction of searching for new thermoelectric materials
Doping of p-ErNiSb semiconductor by Sc atoms by substitution of Er atoms is accompanied by the occupation of vacancies in position 4a
Occupation of vacancies by Sc and Ni atoms leads to an increase of the concentration of free electrons, an enlarge of the compensation degree of semiconductor, which changes the position of the Fermi level εF and the mechanisms of electrical conductivity
Summary
Important components of modern research are both experimental results obtained using a variety of highly efficient equipment and theoretical studies that describe, explain experimental data, and, in most cases, serve as a basis for the predictive search for new materials and optimization of their functional characteristics. Experimental studies of thermoelectric semiconducting solid solution p-Er1-xScxNiSb, x = 0 - 0.10, (MgAgAs structure type, space group F4 ̄3m [7]), obtained by doping the semi-Heusler phase p-ErNiSb by neutral impurity Sc introduced by substitution of the rare earth metal atoms Er in 4a position, revealed the appearance of donors of unknown origin [8]. 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. In the present work, based on previously obtained experimental data [8], the results of modeling the thermodynamic, structural, energetic, and electrokinetic characteristics of the p-Er1-xScxNiSb semiconductor, x = 0 - 0.10, synthesized by doping of p-ErNiSb by Sc atoms due to substitution of Er atoms (4a position), were presented. The obtained results allow to refine the spatial arrangement of atoms (or their absence) in the nodes of the unit cell, and to identify the mechanisms of electrical conductivity to determine the conditions of synthesis of thermoelectric materials with maximum efficiency of conversion of thermal energy into electricity
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