Papers by Keyword: Ag₂Se

Abstract: Ag₂Se nanocrystal was successfully prepared by ultrasonic synthesis in water and ethanol systems at an ambient pressure. The powder of selenium was used as the selenium ion source. The size of the nanocrystals is in the scope of 10-20nm. The products were characterized by some means including X-ray Powder Diffraction (XRD) and Transmission Electron Microscopy (TEM) which was used to study the thermostability of the product. The result of the experiments indicated that the concentration of the reactant, the pH of the solution, the react temperature and the surfactant had some important influence on the formation and the size of the Ag₂Se nanoparticles. The method we reported here is proved to be a new and an easy way to prepare the nanocrystals of metal chalcogenide.

Abstract: The thermoelectric properties of Ag2Se and excess Ag alloys synthesized by mechanical alloying process were studied. The absolute S value slightly decreased with the Ag content. Contrary to that, the electrical conductivity (σ) increased with the Ag content. This was due to the increased carrier concentration supplied by the excess Ag clusters. Below 280K, the σ value of the excess Ag alloys is almost constant regardless of temperature, which means that the Ag excess alloys is highly degenerated. At higher temperatures above 290 K, the intrinsic conduction behavior for all materials is observed and the band gap energy for Ag2Se calculated from the slope of curve in this higher temperature range is about 220 meV. The figure of merit value (Z) was increased by the excess Ag, from 0.28/K (Ag2Se) to 0.91/K (Ag2.05Se0.95).