Rapid Synthesis,Microstructural Regulation And Thermoelectric Transport Performances Of In-filled CoSb₃ Skutterudites

In recent years,increasing energy consumption and increasingly serious environmental problems have attracted widespread attention.To overcome the upcoming energy crisis,it is of great significance to explore sustainable and eco-friendly energy resources.Thermoelectric materials and devices,based on the direct conversion between thermal energy and electrical energy,have been considered as promising alternatives to meet the challenges of the global energy dilemma.Skutterudite is one of the most promising intermediate-temperature thermoelectric materials and has attracted wide attention from all over the world.The binary skutterudite molecular formula is expressed as AB₃,where A is a transition metal element such as Fe,Co,Rh,Ni,and B is a phosphorus group element such as Se,Sn,Sb,and Te.Due to the high thermal conductivity of CoSb₃-based skutterudite material,its thermoelectric figure of merit is low,which limits the practical application of skutterudite in the thermoelectric field.Currently,doping,filling,High-energy ball milling compound,and other methods to optimize its thermoelectric performance.The traditional preparation methods of CoSb₃-based skutterudite thermoelectric materials include high-temperature smelting-annealing,mechanical alloying,high pressure and high-temperature,etc.The process of high-temperature smelting and synthesis requires more than ten hours of high temperature.The melting and boiling point difference between the element and the Sb element is too large,which will eventually lead to the volatilization of a single element in advance,and long-term annealing will lead to excessive growth of crystal grains and increase the preparation cycle.Mechanical alloying lasts for tens of hours or more,which also severely prolongs the sample preparation cycle.Impurities are easily introduced in the ball milling process,and the requirements of the ball milling device are relatively high.In this paper,the In-filled CoSb₃-based skutterudite thermoelectric material was successfully synthesized by the microwave synthesis method,and In atoms were successfully filled into the CoSb₃ lattice.Studies have shown that,compared with unfilled samples,the resistivity of In-filled CoSb₃ samples is significantly reduced,and the carrier concentration is increased by 1000 times,which effectively improves the electrical properties of the material.Filling with In can cause fluctuations in the quality and volume of beaten.Enhance the phonon scattering phenomenon and reduce the thermal conductivity of the material.In this paper,four samples of In_xTe_0.5Co₄Sb₁₂(x=0.4,0.5,0.6,0.8)were prepared with Te_0.5 doping as an invariant.The Te-doped sample and the undoped sample were compared,and the effect of Te doping on the thermoelectric properties of the In-filled sample and its solid solution limit were explored.Among them,the In_0.5Te_0.5Co₄Sb₁₂sample has the highest thermoelectric figure of merit because of its moderate power factor and thermal conductivity,reaching 0.87 at 775K.Compared with the undoped samples,the Seebeck coefficient is limited due to the solid solution limit of In filling,and the thermoelectric performance is not improved.Based on the successfully filled samples,the effect of annealing on the In single-filled samples was studied.Five samples of In_xCo₄Sb₁₂(x=0.4,0.6,0.8,1.0,1.2)were prepared.The annealed samples and unannealed samples were compared,and the effect of the annealing process on the properties of In-filled CoSb₃-based skutterudite thermoelectric materials was explored.Due to the higher power factor and lower thermal conductivity,the thermoelectric figure of merit of the annealed sample is significantly better than that of the unannealed sample.Among them,the thermoelectric figure of merit of the In_0.6Co₄Sb₁₂ sample is the highest,reaching 1.15 at 775K,and the growth trend continues.