Preparation Of CoSb₃ Compounds And Improvement Of Their Thermoelectric Properties

The thermoelectric material is a functional material that can recycle the lost heat energy.The study of thermoelectric materials in the new energy field is very significant.The thermoelectricity value of traditional thermoelectric materials is not ideal enough,resulting in little progress in thermoelectric materials.In recent years,the discovery of some new thermoelectric materials has attracted the attention of scientific researchers.Among them,skutterudite is a typical material,and Co Sb ₃compound is a skutterudite material.Its Seebeck coefficient and electrical conductivity are higher than that of the same type of skutterudite,but its lack of thermal conductivity is also high.Research on lowering its thermal conductivity has attracted widespread attention from researchers.?1?In this paper,the preparation process of Co Sb ₃ compound was studied firstly.The Co Sb₃ intermetallic compound was prepared by ball milling-annealing-SPS method.The ball ratio,ball milling time,annealing and sintering process in ball milling were investigated.The comparison of the XRD patterns of the ball-milled samples with 10:1 and 20:1 ball-to-ball ratio revealed that the larger ball-to-grain ratio can greatly reduce the time for alloying the samples.In the 20:1 ratio,the diffraction peaks of Co Sb₃ can be observed after 10 hours of ball milling.When the ball was ground for 40 hours,three diffraction peaks of Sb,Co Sb ₂,and Co Sb₃ were found,indicating that although mechanical alloying can obtain Co Sb ₃,Compounds,but not a single Co Sb₃ compound,were obtained.After the ball-milled powder was annealed at 650°C,it was converted into a single Co Sb ₃ compound.Then the sample was sintered using the SPS sintering process to obtain a Co Sb ₃ intermetallic compound with better density..?2?The thermoelectric properties of Co Sb₃,Co_3.5Ni_0.5Sb_11.5Te_0.5 compounds were explored.Firstly,the simulation was performed using Material studio software.The Castep module was selected for the simulation experiment.The energy band and density of states of the Co_3.5Ni_0.5Sb_11.5Te_0.5 compound model were calculated at the same time.The results show that the band gap value of the Co _3.5Ni_0.5Sb_11.5Te_0.5compound is smaller than that of the Co Sb₃ compound,and the Fermi level shifts in the direction of the conduction band.The substitution atoms play a role in the total density of states of the matrix,and show that The surrogate compound will exhibit the properties of an N-type semiconductor.Secondly,Co Sb₃ and Co_3.5Ni_0.5Sb_11.5Te_0.5compounds were prepared by ball milling-annealing-SPS method.The thermoelectric properties in the 300-800K temperature range were tested.The results show that the power of Co_3.5Ni_0.5Sb_11.5Te_0.5 compounds The factor reaches a maximum value of1.94×10^-3W·m^-1·K^-2 at 750K,and its thermal conductivity is only 2.8W·m^-1·K^-1 at700K,and its thermoelectric value ZT is at 800K.At the time of reaching 0.516,the ZT of thermoelectricity was 9.5 times higher than that of the Co Sb ₃ compound.?3?Explore the effect of filling and substitution on the thermoelectric properties of Co Sb₃ compounds.At present,there are few studies on the filling of In atoms,and the Co Sb₃ compounds filled with Ba and In have a thermoelectric figure of merit of800 or more and 1.0 or more.The effects of In filling and su bstitution of Ni and Te on the thermoelectric properties of Co Sb₃ compounds were investigated.The thermoelectric value of In_0.3Co_4-x-x Ni_x Sb_12-y2-y Te_y compounds was studied.The thermoelectric value of In_0.3Co_3.5Ni_0.5Sb_11.5Te_0.5 compounds was at 750K.The maximum value was obtained with a ZT value of 0.62.The effects of Yb filling and Ni and Te substitution on the thermoelectric properties of Co Sb ₃ compounds were investigated.With the replacement of rare earth Yb atoms and substitution of Ni and Te atoms,the absolute values of the conductivity and Seebeck coefficient of Yb_0.3Co_4-x-x Ni_x Sb_12-y2-y Te_y compounds have increased,and the thermal conductivity of the compounds has been greatly reduced.The effect is beneficial to improve the thermoelectricity value of the compound.When the Yb_0.3Co_3.5Ni_0.5Sb_11.5Te_0.5compound is 750K,the maximum thermoelectric value is 0.75.