Study Of The Preparation Of Cu₂S Thermoelectric Material

With the rapid development in the world’s science and technology,the energy’s demand was also increasing day by day.Although the utilization technique of energy is constantly improved and the use ratio of energy increases in this situation,it still imposes negative effects to nature,resulting in the global environmental problem.The device constituted by thermoelectric materials possess features of thermoelectric power generation and thermoelectric cooling,which take full advantage the heat of environment.As the important part of device,thermoelectric material can do the mutual conversion between thermal energy and electrical energy.Copper（I）sulfide has been studied a lot in recent years,and it is a typical“phonic liquid-electric crystal”type material with the extreme low thermal conductivity and moderate thermoelectric properties.It can be a very promising thermoelectric material.This study takes Cu₂S the research object to investigate the effects of the powder for different preparation’s conditions of the chemical precipitation method on the phase and morphology.The correlation between the different content（weight%）SiC and the thermoelectric properties of Cu₂S-SiC composites has been analyzed.Further,the effect of ball milling conditions on the thermoelectric properties of composite samples has been systematically explored.Cu₂S and Cu₂S-SiC composite thermoelectric materials with excellent thermoelectric properties were obtained.Cu₂S nano powder has been prepared by a chemical precipitation method.Because the yield by this way is few,about 0.1 g,this research increases the raw amount of reactant by 6times so that the production of reaction can reach about 1 g.This made the whole work more efficiently.After increasing the raw amount of reactant,the research compared the XRD patterns and SEM graphs of the samples by different stirring rates and holding reaction times.The optimal reaction condition can be found.The Cu₂S nano powder was prepared under these optimal technique conditions,then the bulk material was produced by vacuum hot press system and its thermoelectric properties were characterized.The result shows that the ZT of the Cu₂S bulk material reaches 0.23 at the temperature of 760 K.In order to gain an improvement in thermoelectric properties,this article comes up with a way by using mechanical ball milling to prepare composites of Cu₂S and different content of SiC.Then the composite powder was sintered into the bulk material by vacuum hot pressing.The thermoelectric properties have been further characterized.After compounding SiC,the electric conductivity of Cu₂S-SiC composite is larger in the low temperature phase.As the temperature increases,the electric conductivity decreases first,and then increases after 700 K.All the Seebeck coefficients of Cu₂S-SiC composites improve with the temperature increases,and the thermal conductivity increases slightly when the content of SiC increases.Conclusively,Cu₂S-4 wt%SiC material gets the best thermoelectric property among samples,and the ZT value attains 0.55 at 760 K.To specifically explore whether the thermoelectric property of Cu₂S-SiC can be improved further,this work investigated the effect of different ball milling speed and ball milling times on the thermoelectric property of the Cu₂S-SiC sample with 4 wt%SiC included.Under the circumstance of changing ball milling speed only,it is found that the thermoelectric property of sample declines with the ball milling speed increase.The main reason lies in the declination of the electric conductivity.On another condition of changing ball milling time only,the ZT value of the sample decreases with the ball milling time increase.The overall trend of the ZT value is to increase firstly,then decrease,and then increase as the temperature increases.The maximal ZT value can be obtained with the ball milling time of 1 h.With the circumstance of ball milling speed at 200 rpm and ball milling time of 1 h,Cu₂S-4 wt%SiC sample’s ZT value can reach the maximum of 0.87.