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

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. Electrical conductivity measurements showed metallic conduction behaviour besides a tremendous decrease in its values with increasing Ag content (x). In contrast, Ag-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, specially at higher Ag-content. The largest ZT value was recorded at 0.25, achieved for Cu1.93Ag0.07Se at 473 K, which is about two times of that observed for the pristine Cu2Se sample. The overall findings of the current study clearly demonstrates that the increasing of the Ag content helps to obtain good TE properties of the cubic Cu2−xAgxSe system, specially at higher temperatures.