Transport and thermoelectric properties of crystalline Cu2-xAgxSe alloys prepared by facile method

Abstract

Abstract Crystalline alloys of Cu2-Se containing a transition metal, earth-abundant and eco-friendly element, are studied in this article as promising eco-friendly thermoelectric materials. Thermoelectric and transport properties of Cu2-xAgxSe (x = 0.00, 0.01, 0.03, 0.05, 0.07) bulk alloys were studied in the temperature range 273-473 K. Crystal structure and surface morphology were tested by X-ray diffraction analysis and scanning electron microscope analyses. Electrical conductivity measurements showed metallic conduction behaviour besides a tremendous decrease in its values with increasing Ag content (x). In contrast, doping increased the Seebeck coefficient to a large extent. Calculations of the electronic thermal conductivity showed that phonon scattering is increased due to the Ag-doping. The incorporation of Ag-atoms resulted in existence of point defects, introduced secondary phases which significantly reduced the thermal conductivity. Such effects resulted in enhanced ZT by the excess Ag-content. The largest ZT value of 0.25 was achieved for x = 0.07 at 473 K, which is about two times of that of the pristine Cu2Se sample. Increasing of the Ag content helps to maintain good TE properties of cubic Cu2-xAgxSe at higher temperatures.