This review presents thermoelectric phenomena in copper chalcogenides substituted with sodium and lithium alkali metals. The results for other modern thermoelectric materials are presented for comparison. The results of the study of the crystal structure and phase transitions in the ternary systems Na-Cu-S and Li-Cu-S are presented. The main synthesis methods of nanocrystalline copper chalcogenides and its alloys are presented, as well as electrical, thermodynamic, thermal, and thermoelectric properties and practical application. The features of mixed electron–ionic conductors are discussed. In particular, in semiconductor superionic copper chalcogenides, the presence of a “liquid-like phase” inside a “solid” lattice interferes with the normal propagation of phonons; therefore, superionic copper chalcogenides have low lattice thermal conductivity, and this is a favorable factor for the formation of high thermoelectric efficiency in them.

This paper presents an experimental study of the electronic thermoelectric power as a function of copper content for LixCu(2−x)−δS (x ≤ 0.25) electronic-ionic mixed conductors. Using a vacancy model f

The paper presents and discusses the results of experimental studies of the electronic conductivity, Seebeck coefficient and thermal conductivity of KxCu2−xS alloys (x = 0.1, 0.2, 0.25) in the temperature range from 30 to 420°C. According to the results of X-ray phase analysis, the alloys are mixtures of various phases of copper sulfide: the cubic Fm-3m phase Cu1.84S, cubic Fm-3m phase Cu2S, rhombohedral R-3m phase Cu17S9, and metastable tetragonal P43212 phase Cu2S.

The paper presents the studies of ionic and electronic Zeebeck coefficients and electronic conductivity in nonstoichiometric Ag_0.25–δCu_1.75Se, Ag_1.2–δCu_0.8Se solid solutions existing on the basis of the cubic phase of copper selenide. It is shown that Ag_1.2–δCu_0.8Se is a bilateral variable composition phase manifesting inversion of the sign of predominant charge carriers under variation of the chemical composition by silver within the homogeneity region. Mobilities of electrons and electron holes are estimated on the basis of the concentration dependences.

Copper sulfide is a multifunctional material. Copper sulfides are known to be used in photo-electric converters, in plasmonics, in active electrodes of batteries and supercapacitors, etc. The excellent thermoelectric properties of copper sulfide are well-known too. The purpose of this study is to investigate the thermoelectric performance of nanocomposite copper sulfide contained monoclinic Cu₂S and tetragonal Cu_1.96S phase. According to scanning electron microscopy, the average particle size of the synthesized powder was about 373 nm. The Li_0.11Cu_1.89S sample showed an electronic conductivity of 50–180 S/cm, a Seebeck coefficient of 0.04–0.31 mV/K in the range of 300–700 K, and high power factor 5.8 μW K⁻²cm⁻¹ at 672 K. Total thermal conductivity decreases with increasing temperature from 0.61 to 0.22 W∙K⁻¹m⁻¹ in the range of 300–700 K. Such low thermal conductivity and high power factor made it possible to achieve an extremely high dimensionless thermoelectric figure of merit ZT = 1.76 at 672 K, which allows to consider the Li_0.11Cu_1.89S alloy as a promising thermoelectric material.