Study On Preparation Of CoSb₃ Nano-powders By Hydrothermal/Solvothermal Method And Properties

There are many kinds of thermoelectric materials,which are relatively classic in the middle temperature zone and the commonly used thermoelectric materials are skutterudite thermoelectric materials.Since the concept of"phonon glass-electron crystal"?PGEC?was proposed by Dr.Slack in 1995,the research direction of thermoelectric materials has been greatly expanded.In order to improve the thermoelectric conversion efficiency,the quality factor?ZT value?of the skutterudite thermoelectric material is the focus of research.The main ideas for improving the ZT value of thermoelectric materials include reducing thermal conductivity,increasing conductivity and increasing power factor.The main methods include filling,low-dimensional nanostructures,and composite equalization.The principle is to increase the number of grain boundaries and form an energy barrier at the grain boundaries.The energy filtering effect is used to scatter low-energy phonons to improve the effective mass and concentration of the carriers,thereby increasing the ZT value of the thermoelectric material.In this paper,the nano-powder preparation of skutterudite and the filling of rare earth elements and alkaline earth metal elements can be used to realize the nanostructure of the skutterudite matrix material,and at the same time realize the nanostructure of the material itself and the nano-engineering through the recombination of the nano-second phase,thereby improving the thermoelectric properties of the skutterudite,ie the ZT value.Firstly,the high-purity and uniform size of CoSb₃nanopowders were prepared by hydrothermal/solvothermal method by adjusting the process parameters,including temperature,time,raw material ratio and raw material pre-hydrolysis reaction.The influencing factors were analyzed for CoSb₃ nanopowders.The effects of purity,size and morphology provide basic experimental conditions for the subsequent filling of rare earth elements and alkaline earth metal elements.The specific research contents and results are as follows:?1?CoSb₃ nanopowders were prepared by hydrothermal/solvothermal method under high temperature and high pressure conditions.The best experimental conditions were obtained by XRD pattern and SEM image analysis.The holding temperature was290°C,the temperature was kept for 12 h,and the ratio of raw materials was 1:3.The spherical particles with a purity of 86.3%and a size of 50-70 nm can be prepared under the reaction conditions of pre-hydrolysis of raw materials;and the results of XRD pattern analysis are combined to give the reaction at various stages in the synthesis of CoSb₃ nanopowder;When the ratio of raw materials is Co:Sb=1:3,the morphology of the product is spherical particles;when the ratio of raw materials is Co:Sb=1:3.5,the morphology of the product is square;?2?Using the hydrothermal/solvothermal method to fill the cobalt ore with rare earth elements and alkaline earth metal elements,and explore the best experimental conditions;Ba_xFe₄Sb₁₂ nanopowder can be prepared under the experimental conditions of holding temperature of 290°C and holding time of 12 h;Ba_xCo₄Sb₁₂ nanopowder can be prepared under the experimental conditions of holding temperature of 290°C and holding time of 24 h;XRD pattern analysis results in the chemical reaction involved in the synthesis of Ba_xCo₄Sb₁₂ nanopowder;?3?According to the phase and morphology analysis of the product obtained from the experiment,the reaction mechanism of the CoSb₃ series nanopowder prepared by hydrothermal/solvothermal method was given.