Abstract:
The conditions for the synthesis of compounds based on rare earth elements (REE) of the compositions Y$_2$O$_3$@SmS, (Y$_{0.90}$Gd$_{0.10}$)$_2$O$_3$@SmS and (Y$_{0.99}$Gd$_{0.01}$)$_2$O$_3$@SmS were optimized with a core-shell type nanostructure. The optimization process consisted in finding the minimum times and optimal temperatures at each stage of synthesis to stabilize the phase of Y and Gd oxides, as well as complete conversion to SmS in the studied composites after successive stages of sulfidation and annealing of the initial precursors. The thermoelectric properties in the temperature range $T$ = 298–873 K were studied and compared with the literature data for thermoelectric compounds based on REE. For connection (Y$_{0.99}$Gd$_{0.01}$)$_2$O$_3$@SmS at $T$ = 873 K, the values of the Seebeck coefficient $S$ = -94 $\mu$V/K, the resistivity $\rho$ = 17 $\mu\Omega$$\cdot$ m and the total thermal conductivity coefficient $\kappa_{\mathrm{tot}}$ = 1.50 W/m $\cdot$ K. The maximum achieved value of the thermoelectric $ZT$ parameter for the connection (Y$_{0.99}$Gd$_{0.01}$)$_2$O$_3$@SmS reaches values of $ZT$ = 0.56 at $T$ = 873 K, which is a promising result in comparison with other thermoelectrics based on rare earth elements.
Keywords:REE oxides and sulfides, sol-gel synthesis, core-shell, topological reactions.
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