Thermoelectric and Magnetic Properties and Electronic Structure of Solid Solutions CuCr1-xLaxS2

Abstract

The oxidation states of atoms in CuCr1-xLaxS2 (x = 0–0.03) solid solutions were determined using the analysis of Cu2p, Cr2p, S2p, and La3d core level binding energy. The cationic substitution did not significantly affect the charge distribution on matrix elements (Cu, Cr, and S). The oxidation states of the atoms were identified as S2− for sulfur, Cu+ for copper, and Cr3+ for chromium. The cationic substitution in CuCr1-xLaxS2 was found to occur via the isovalent principle. The cationic substitution of CuCrS2 matrix with lanthanum ions led to the enhancement of the Seebeck coefficient comparing CuCr1-xLaxS2 to the initial matrix. The observed enhancement was attributed to the reconstruction of the valence band electronic structure after the cationic substitution. The maximum Seebeck coefficient value of 412 μV/K was measured for CuCr0.985La0.015S2 at 420 K. An increase in the lanthanum concentration to x = 0.03 caused a suppression of the Seebeck coefficient. The synthetic route was found to significantly affect both the magnetic properties and charge carrier concentration. The magnetic properties of CuCr1-xLaxS2 synthesized using metal sulfide reagents cannot be interpreted using the simple isovalent Cr3+ to La3+ cationic substitution model. The defectiveness of the samples and the formation of the impurity CuLaS2 phase could be additional factors that affect the magnetic properties of CuCr1-xLaxS2.

Thermoelectric Properties of Layered CuCr0.99Ln0.01S2 (Ln = La…Lu) Disulfides: Effects of Lanthanide Doping

“…For instance, the binding energy of the 4f -levels increases with the lanthanide atomic number. Note that an increase in the substitution concentration causes Seebeck coefficient suppression due to the metal-insulator transition (MIT) [32,33]. An increase in the lanthanide concentration to x = 0.03 results in the presence of an additional CuLnS 2 impurity phase in the composition of CuCr 1−x Ln x S 2 , as was previously shown for lanthanum [33].…”

“…suppression due to the metal-insulator transition (MIT) [32,33]. An increase in the lanthanide concentration to x = 0.03 results in the presence of an additional CuLnS2 impurity phase in the composition of CuCr1−xLnxS2, as was previously shown for lanthanum [33]. The Seebeck coefficient value increases as a function of the lanthanum concentration up to x = 0.015.…”

“…suppression due to the metal-insulator transition (MIT) [32,33]. An increase in the lanthanide concentration to x = 0.03 results in the presence of an additional CuLnS2 impurity phase in the composition of CuCr1−xLnxS2, as was previously shown for lanthanum [33].…”

“…The combination of the aforementioned properties allows CuCrS 2 -based compounds to be considered promising materials for the fabrication of high-performance thermoelectric generators (TEGs). The cationic substitution of the CuCrS 2 -matrix is significantly affected by the thermoelectric properties of the initial matrix [32][33][34][35][36]. It was previously reported that the cationic substitution of the CuCrS 2 -matrix with a low concentration of doping atoms could enhance the thermoelectric properties of the initial matrix.…”