Study On Preparation Of Sb₂Te₃ And Sb₂Se₃ Nanomaterials By Microwave Heating And Wet-chemical Method

Thermoelectric materials, which could be used to achieve the direct transfer between thermal energy and electric energy, are new functional materials with peculiar significance.With the development of nanotechnologies and relevant theories, their thermoelectric performance has been improving rapidly in recent years. Due to their stronger quantum confinement effect, it has been expected that one-dimensional thermoelectric nanomaterials(nanorod, nanotube, nanoline, etc) have more excellent performance than two-dimensional nano films. Currently Bi2Te3-based bulk materials are one of the most widely used thermoelectric materials, and a remarkable progress with ZT=2.4 has been reported in Bi2Te3/Sb2Te3 nano-superlattice system. However, preparation and morphology control to Bi2Te3-based one-dimensional thermoelectric nanomaterials have not been solved. Wet-chemical methods have been tried for preparation bismuth telluride based materials by many researchers, and some successful results have been reported. As a special and effective energy source, microwave heating can greatly reduce the reaction time, and improve the reaction efficiency, furthermore the effect of microwave heating is could eliminate temperature gradient and heat uniformly, so it can be helpful to quick nucleation, and it is easy to get uniform nanomaterials. In this thesis, microwave heating has been combined with wet-chemical method to synthesis bismuth telluride based one-dimensional nanomaterials, and nanorods of both Sb2Te3 and Sb2Se3 compounds have been prepared successfully. Reaction parameters and experimental conditions have been fixed and optimized, and this will be helpful to the future research.Without addition of surfactants, single-phase hexagonal Sb2Te3 nanoflakes have been synthesized within 30 minutes, and it has been found that the pH value is the key factor to the experiments, reaction duration could greatly reduced with increasing the pH value of the reactants. .Adding sodium dodecyl sulfate to the reaction system, the morphology of Sb2Te3 products changes and looks like broken leaves, and then some one-dimension Sb2Te3 nanorods were synthesized while dodecyl sulfonic acid sodium salt was used as surfactants. Increasing the surfactant amount of dodecyl sulfonic acid sodium salt, the fraction of Sb2Te3 nanorods increased as well. A possible reaction mechanism and crystal growth mechanism have been suggested.KBH4 is a key factor to the synthesis of Sb2Se3 nanorod. Without addition of surfactants, single phase Sb2Se3 nanomaterials could be synthesized within 60 minutes, they were inhomogeneous quadrangular nanorods. With addition of dodecyl sulfonic acid sodium salt as surfactants, we found Sb2Se3 products became more homogeneous in size and some changed to round rods. Evidently the surfactants were the key factor which brought this change. A possible reaction mechanism and crystal growth mechanism were proposed.