Rapid Synthesis And Thermoelectric Properties Of Ni-doped Skutterudites

With the development of industrialization and the improvement of domestic water products,the requirements for energy in production and life are getting higher and higher.People began to pay attention to the drawbacks of traditional energy sources and seek new energy sources that are more efficient and clean.Thermoelectric material is a functional semiconductor material that can convert thermal energy and electrical energy into each other.It can use less temperature difference in the environment to generate electricity and improve energy efficiency.The skutterudite is a medium temperature thermoelectric material with excellent electrical transport properties,but the higher thermal conductivity affects the thermoelectric properties of the material.How to reduce the thermal conductivity without affecting the electrical properties of the skutterite ore has become the research direction.Doping of dissimilar elements is one of the methods.By doping,the carrier concentration of the skutterudite can be adjusted and point defects can be increased.The electrical transport properties of the skutterudite are regulated and the lattice thermal conductivity is optimized.In this paper,the Ni-doping and Fe and Ni doubly doped skutterudite were prepared by microwave 5 min synthesis combined with SPS sintering.Since the sintering temperature of 903K cannot meet the requirements of the alloying reaction,it can be determined that the doped skutterudite is synthesized by microwave for 5min.Compared with common synthetic methods,microwave heating is more uniform,synthesis time is shorter,and grain growth is avoided.The synthesized skutterudite has uniform composition and high purity and does not require long time annealing.The thermoelectric transport mechanism of the skutterudite was investigated by observing the microstructure of the sample and testing the thermoelectric properties.A Ni-doped skutterudite alloy material was synthesized,and the sample exhibited n-type semiconductor characteristics.As the amount of doping increases,the carrier concentration increases.The maximum power factor of Ni_0.3Co_3.7Sb₁₂2 is2711?Wm^-1K^-2.Doping introduces point defects,refines the grains and enhances phonon scattering.The decrease in the lattice thermal conductivity of the doped sample leads to a decrease in the overall thermal conductivity,which is the result of the combination of point defects and grain refinement.The ZT maximum of the sample moves to the high temperature with the increase of the doping amount,and the ZT value of the sample Ni_0.3Co_3.7Sb₁₂2 is 0.52 at the maximum.Based on Ni_xCo_4-xSb₁₂,we have explored Fe and Ni doubly doped skutterudite.Fe_yNi_0.2Co_3.8-ySb₁₂2 alloy material was synthesized and the sample exhibited n-type semiconductor characteristics.Compared with the doping of Ni element,the resistivity of Fe and Ni double doping decreased significantly,and the power factor increased.Compared with the single doping of Ni element,the resistivity of Fe and Ni double doping decreased significantly,and the power factor increased.The maximum power factor of Fe_0.1Ni_0.2Co_3.7Sb₁₂2 at 687 K is 2666.7?Wm^-1K^-2,and the power factor of Ni_0.2Co_3.8Sb₁₂2 is only 2479?Wm^-1K^-2.The ZT value of the sample Fe_0.1Ni_0.2Co_3.7Sb₁₂2 is 0.50,which is higher than the ZT value of 0.45 of Ni_0.2Co_3.8Sb₁₂.