Preparation And Thermoelectric Properties Of AgSbTe₂ By Sonochemical Method

Cubic AgSbTe2 is not only a promising p-type thermoelectric material on its own but also an important component of several high-performance thermoelectric compounds. Over past years, AgSbTe2 was synthesized by many pursuers using various methods such as Bridgman method, zone melt, high pressure and high temperature etc. Usually these methods demand large duration of heat process or complicated instruments. So, looking for a simple and quick synthesis route will be of great importance.In this paper, we explored the synthesis process of AgSbTe2 compounds by sonochemical method, and then systematically studied the impacts of synthesis and sintering process, deviation of the stoichiometric ratio and alloying with AgBiTe2 on the phase, microstructure and thermoelectric properties. The following results have been obtained in this thesis:(1) The AgSbTe2 single phase was prepared by heat reduction treatment of the precursor which was obtained by sonochemical method. The influence of sonochemicial process, heat treatment process and the initial stoichiometric ratio on the phase of the product has been systemically studied. High relative density single phase bulk materials were obtained after SPS.(2) The study of deviation of the stoichiometric ratio, (Ag2Te)x(Sb2Te3)100-x (x=44-54) compounds:microstructure analyses show that there were 10～50 nm nanoparticles embedded on the grains after SPS, and the phase of the nanoparticles may be Ag2Te. As the increase of x, the electrical conductivity increases gradually, the Seebeck coefficient and the thermal conductivity decrease. For x=48 and x= 50 samples, the maximum power factor reach～1.5 mW/(m·K2) at 400～500K; For x= 50, x=52 and x=48 samples, the thermal conductivity show no clear dependence of temperature, and maintained at about～0.6W/mK; x=50 sample presents the best thermoelectric performance, the maximum ZT reaches 1.55 at 533K, much higher than that of sample prepared by other methods. (3) The study of alloying AgSbTe2 with AgBiTe2:solid solubility of AgBiTe2 in AgSbTe2 is less than 40%. There were no nanoparticles on the surface of the grains after alloying. As the increase of x, the Seebeck coefficient increases gradually, the electrical conductivity and the thermal conductivity decrease; when x=0.1, the minimum thermal conductivity approaches 0.44W/mK at 534K, and the maximum ZT reaches 1.28 at 534K.