N型Yb_xCo₄Sb₁₂热电材料及涂层的制备与性能研究

Bulk Yb_xCo₄Sb₁₂(x=0.27, 0.28, 0.29) alloy samples were prepared by melt-annealing-discharge plasma sintering. XRD, SEM and EDS analysis show that Yb doped single phase CoSb₃ thermoelectric material has been successfully synthesized. When the Yb content increases from 0.27 to 0.29, the power factor of the material increases first and then decreases with the increase of temperature, while the thermal conductivity decreases first and then increases. Due to the relatively high power factor of 1815 μW•m^-1•K^-2 and the relatively low thermal conductivity of 2.23 W•m^-1•K^-1, a higher ZT value of 0.62 of the alloy Yb_0.29Co₄Sb₁₂ is obtained at 773 K. The Al-Ni protective coating of Yb_0.29Co₄Sb₁₂ was sputtered by magnetron sputtering method. SEM and EDS results show that the coating is bonded well with the substrate, and the thermoelectric properties of Yb_0.29Co₄Sb₁₂ element protected by coating have good stability. The welding behavior of the joint between thermoelectric Yb_0.29Co₄Sb₁₂ and electrode Mo₅₀Cu₅₀ was studied with Ag₄₀Cu₆₀ filler metal. It is found that the interface is well bonded and the elements such as Co, Sb, Yb and Mo do not spread seriously at the interface.