Study On The Brazing Process And Mechanism Of Ce-filled N-type Skutterudite And Copper Electrode Joint

Skutterudite material based on CoSb3 is the most promising thermoelectric material in the mid-temperature range(600-900K)for large-scale applications.In theory,it can be used to improve the efficiency of thermoelectric power generation.In thermoelectric devices,the connection between metal electrodes and thermoelectric materials is particularly important.Due to the problems of element diffusion and reaction at the interface,the contact resistance and thermal resistance of the interface will be greatly improved.The best way is to introduce an anti-diffusion barrier layer.It focuses on the process of connecting the barrier layer on the surface of the thermoelectric material and then connecting the electrode.The Ce0.3Co4Sb12 thermoelectric material powder and the CoMo alloy foil are integrated and hot-pressed sintered to prepare a CoMo alloy barrier layer on the surface of the Ce0.3Co4Sb12 thermoelectric material,and the Ce0.3Co4Sb12 thermoelectric material and the Cu electrode are prepared by the AgCuInSn brazing method.For thermoelectric joints,the high-temperature service stability of thermoelectric joints was studied by aging at 550?.The Ce0.3CO4Sb12 thermoelectric material with uniform composition was prepared,and the ZT value reached 0.99.The self-designed CoMo alloy barrier layer is a barrier layer composed of dual-phase alloy M06Co7+MoCo3,which has a good match with the linear expansion coefficient of Ce0.3Co4Sb12 thermoelectric material.By exploring different hot-pressing sintering process parameters and observing the changes of the interface diffusion reaction layer,it is concluded that the hot-pressing sintering temperature is 750?,the hot-pressing sintering pressure is 60MPa,the hot-pressing sintering holding time is 10min.This test is a more suitable hot-pressing sintering process.Parameters,a typical(Mo6Co7+MoCo3)+CoSb+CoSb2+Ce0.3Co4Sb12 hot press sintering interface is obtained,and the thickness of the diffusion reaction layer can be controlled at about 10?m.Test the wettability of the AgCuInSn solder to the barrier layer of the CoMo dualphase alloy at a temperature of 650? and a holding time of 10 minutes.The contact angles ?1 and ?2 on both sides are measured to be 17.4° and 15.2°,indicating that the AgCuInSn solder pair The barrier layer of CoMo dual-phase alloy has good wettability.At a brazing temperature of 620? and a holding time of 10 minutes,the interface is smooth and defect-free.The AgCuInSn brazing filler metal completely fills the brazing seam.The 200?m thick CoMo dual phase alloy barrier layer effectively inhibits the diffusion of Sb and Cu elements.It reacts and forms a good metallurgical bond with the Ce0.3Co4Sb12 thermoelectric material and Cu electrode on both sides.The shear strength of the joint reached the maximum 15.6MPa,the interface structure was obtained as Ce0.3Co4Sb12+CoSb2+CoSb+CoMo alloy(Mo6Co7+MoCo3)+Co(s,s)+AgCuInSn+Cu(s,s)+Cu electrode.After aging at 550? for 50h,the thickness of the interface diffusion reaction layer increased to 13 ?m.With the increase of aging time,at 100h,150h and 200h,the thickness of the interface diffusion reaction layer increased to 15?m,16?m and 17?m,respectively,and the growth rate gradually decreased.The shear strength of thermoelectric joints after aging for 50h was 13.2MPa,and when the aging time increased to 100h,150h,and 200h,the shear strength of thermoelectric joints changed little,and they were all about 12MPa.The relationship between the interface diffusion reaction layer thickness L(?m)and the aging time t(h)is fitted as follows:L=10+0.5?t.The interface contact resistance of thermoelectric joints when directly brazed without aging treatment is as low as 8.52??·cm2,and the interface contact resistance of thermoelectric joints after aging treatment at 550? for 200h is 14.31??·cm2,indicating that the thermoelectricity prepared by the test is in service at 550? The joint has high temperature reliability.