Interface Optimization And Transport Perfromace Of Interlayer To Pb Te-based Thermoelectric Joint

In recent years,energy consumption has become increasingly serious and environmental pollution problems have gradually intensified.In order to overcome the upcoming energy crisis,it is important to find alternative clean energy sources.The thermoelectric conversion technology which is based on the direct conversion of heat and electric energy is considered to be a promising substitute for fossil energy,thus coping with the global energy dilemma.Thermoelectric modules have the advantages of environmental friendliness,strong safety performance,simple operation and maintenance,etc.The important application prospects in industrial waste heat recovery,aerospace,national defense,deep-sea fields,and aerospace are also been valued.The key step for thermoelectric modules to meet the application standards is to realize the effective connection between the thermoelectric material matrix and the electrode material,through the optimization technology of interface performance to realize the efficient and sustainable application of thermoelectric connectors.Therefore,the performance of thermoelectric connectors directly determines thermoelectric service life of the device.In this paper,the starting point is to improve the interface performance of the thermoelectric joint with the interlayer material,at the same time the influence of the two interlayer materials on the interface and the whole of the PbTe-based thermoelectric joint is studied.Aiming at the principle of PbTe doping modification,the non-stoichiometric ratio of PbTe was optimized successively.It is found that by adjusting the stoichiometric ratio of PbTe,the intrinsic sample Pb_50.01Te_49.99 with the best thermoelectric performance is obtained,which proves that excessive Pb can achieve a preliminary increase in the carrier concentration of intrinsic PbTe.On this basis,I doped to replaceTe to achieve a further increase in the carrier concentration,and the second phase deposition of Pb I and the dual-phase replacement of Sb were studied to improve the performance of n-type PbTe-based thermoelectric materials.It proves that donor doping and second phase deposition can obtain high-performance PbTe.Since the interface performance of thermoelectric joints is an important factor affecting the quality of thermoelectric devices,this experiment studied the intrinsic PbTe/Fe interface from the perspective of gradient connection.The study found thatTe and Pb were mixed in the Fe electrode and combined with Pb_50.01Te_{49 99} one-step hot press sintering to obtain the required PbTe thermoelectric electrode joints.The results of the study found that the composite electrode will form a mixed intermediate layer of PbTe and Fe.Compared with the pure Fe connection,the contact resistance has a nearly 75%reduction to 26.61??·cm².At the same time,the shear strength is also greatly improved compared with pure Fe electrode,which proves that the mixed intermediate layer of PbTe+Fe can effectively improve the mechanical and electrical properties of thermoelectric joints.On this basis,the use of I-doped PbTe and compound FeTe to form a mobile PbTe-based thermoelectric joint Pb_1.0004Te_0.997I_0.003/FeTe,the study found that FeTe and Pb_50.01Te_49.99 have a smaller work function and thermal expansion coefficient compared with Fe and Pb_1.0004Te_0.997I_0.003.The interface contact resistance of FeTe and Pb_1.0004Te_0.997I_0.003 is smaller after being connected.The shear strength is 11??·cm²,the shear strength is23 MPa,and there is no violent diffusion of elements and the formation of reaction layer at the interface.After 573 K 400 h high temperature aging,the electrical and mechanical properties of the interface remain stable.The joint FeTe/Pb_1.0004Te_0.997I_0.003/FeTe showed higher output power and conversion efficiency than Fe/Pb_1.0004Te_0.997I_0.003/Fe.The interface contact resistance formed by the material(or intermediate layer material)and the thermoelectric material Pb_1.0004Te_0.997I_0.003 is different.Although the resistivity of Fe is low,FeTe/Pb_1.0004Te_0.997I_0.003/FeTe forms a smaller interface contact Resistance,so there is a higher output power and conversion efficiency,its maximum output power is 0.025 W,the maximum conversion efficiency is 0.26%.Therefore,FeTe is an excellent interlayer material between Pb1.0004Te0.997I0.003 and Fe.