Investigation of thermoelectric properties of nanocrystalline copper chalcogenides

Abstract

Modern research efforts are aimed at developing fuel cells characterized by high efficiency, low cost and environmental friendliness, which largely depend on the properties of the corresponding catalyst materials ― the most important components of the fuel cell. Catalysts based on metal chalcogenides, predominantly S based, have activity in accelerating the oxygen reduction reaction comparable to the activity of Pt in H₂SO₄. The work uses the technique of compacting powder materials and obtained volumetric samples. Nanodisperse powder fractions with an average particle size of (50–100) nm were obtained. The values of the thermo-emf coefficient (about 0.08 mV/K) were obtained for the studied alloy with low defects in the cation sublattice of the Сu₂S_0.5Te_0.5 type. It was found that a decrease in grain size leads to a significant decrease in electronic conductivity for all studied samples. The paper presents the results of a study of the thermoelectric properties of the Cu₂S_0.5Te_0.5 triple alloy. For the studied composition, a decrease in thermal conductivity by (25‒30)% and a slight increase in the thermal emf coefficient compared with large–crystal samples were obtained. Low thermal conductivity was found in the range (0.3–1.1) W m^-1 K^-1 with a conductivity above 1000 ohms-1cm-1. For the studied sample Cu₂S_0.5Te_0.5  ― thermoelectric efficiency (ZT = 0.25) at 400 °C, which allows us to hope for the possibility of improving the characteristics of samples of this composition to acceptable values for practical thermoelectric devices by selecting the optimal alloying.