Microstructure And Properties Of The Skutterudites Thermoelectric Materials And Joints

The skutterudite has good thermoelectric properties and excellent mechanical properties and is the most practical medium-temperature thermoelectric material.For the preparation of thermoelectric devices,p-type and n-type connectors are equally important.To obtain high-performance thermoelectric devices,not only excellent thermoelectric materials but also high-quality connections are required.At present,the thermoelectric properties of p-type skutterudite are much lower than that of ntype skutterudite,and the connection of p-type skutterudite has not yet been effectively solved.Therefore,obtaining high performance and low cost p-type skutterudite material and reliable connection has great practical value.In this dissertation,based on La0.8Ti0.1Ga0.1Fe3 Co Sb12 skutterudite material,the substitution of Ce for a part of La further reduces the lattice thermal conductivity and improves the thermoelectric properties.At the same time,the preparation of the p-type skutterudite high-temperature joint and the low-temperature joint is studied.,Examine the high temperature end joint under service conditions.Get the following results:The La0.8-x Cex Ti0.1Ga0.1Fe3 Co Sb12 material was prepared by melt annealing and hot-pressing sintering.The grain size of the alloy was 10-20 ?m.When the Ce content was greater than or equal to 0.6,second phases appeared in the material.The actual filling amount decreases with increasing Ce content;Ce filling has little effect on the electrical transport properties of the material,further reducing the lattice thermal conductivity of the material.The ZT value of La0.4Ce0.4Ti0.1Ga0.1Fe3 Co Sb12 material reached 1.05 at 723 K,and the average ZT value of 300-773 K was 0.72.The connection of p-type skutterudite and Fe Cr Ni barrier materials was achieved by one-step sintering.The analysis results show that there are obvious reaction layers in the p-SKD/Fe Cr Ni interface,mainly the diffusion of Sb,Fe and Ni elements.The preparation of p-type skutterudite high-temperature end joints was achieved using Ag-Cu-Zn-Sn solder.With the increase of brazing temperature,the width of the pSKD/Fe Cr Ni interface reaction layer increased;Fe Cr Ni/Ag-Cu-Zn-Sn The interfacial diffusion increases;the joint shear strength increases,the contact resistivity decreases first and then increases;when the brazing temperature is too high,cracks,voids and Fe Sb2 secondary phases appear at the p-SKD/Fe Cr Ni interface.,Optimized to get high temperature end joint brazing connection temperature is 660 °C.Under the service conditions,the joints at the high temperature end were tested.The results showed that after a long time aging,the interface of the thermoelectric contact was good and there was no obvious change;the shear strength of the thermoelectric joints did not change significantly,and the contact resistance increased,but it could meet the requirements of the device.Using Pb-Sn solder to achieve the preparation of p-type skutterudite lowtemperature joints,the analysis results show that p-SKD/Pb-Sn/Mo Cu interface is well-bonded,no cracks and holes,contact resistance is 2.8??·cm2,shear strength Up to 11 MPa,to meet the device requirements.