Mechanochemical synthesis of eucairite CuAgSe and investigation of physicochemical and transport properties

Copper silver selenide, CuAgSe, was easily and conveniently prepared from Cu, Ag and Se powders in a stoichiometric ratio by one-step solvent-free mechanochemical synthesis after 7 min of milling in a planetary ball mill. The kinetics of the synthesis, along with the structure, morphology, thermal stability, physicochemical, and thermoelectric properties of the product were investigated. The crystal structure, physicochemical properties, and morphology were characterised by X-ray diffraction, particle size distribution analysis, specific surface area measurements, X-ray photoelectron spectroscopy, and scanning and transmission electron microscopy. XRD confirmed the crystal structure as a mixture of tetragonal and orthorhombic CuAgSe. Analysis of surface composition revealed partial surface oxidation. Electron microscopy revealed that the nanostructured product consisted of agglomerated particles of irregular shape which formed clusters with a size >20 μm while the mean size of crystallites was 12.1 nm. The mixed crystal structure was also confirmed by selected area diffraction. Thermal analysis clearly indicated a reversible phase transformation. The spark plasma sintering method was applied to prepare a dense CuAgSe pellet for thermoelectric characterization. High-temperature transport properties were examined to assess the potential application of mechanochemically synthesized synthetic eucairite in energy conversion.