Interfacial Reactions in Ni/Sb 2 Te 3 and Co 0.2 Ni 0.8 /Sb 2 Te 3 Couples

Sb 2 Te 3 is an important thermoelectric material. The interfacial reactions in the Ni/Sb 2 Te 3 and Co 0.2 Ni 0.8 /Sb 2 Te 3 couples are examined to verify if Ni and Co 0.2 Ni 0.8 are suitable barrier layer materials. The Ni-Sb-Te phase equilibria isothermal sections and Co-Ni-Sb-Te isothermal tetrahedrons are proposed to provide fundamental information and for better understanding of the interfacial reactions. Only one reaction phase, λ 2 -NiSb 1−x Te 2x , is observed in the Ni/Sb 2 Te 3 couples reacted at 200°C, 300°C, and 400°C. When reacting at 500°C for 6 h, the reaction phase is λ 1 -Ni(Sb 1−x Te x ) 1+y . With a longer reaction time, the second phase, Ni 5.66 SbTe 2 , is formed. Note, the compositional ratios of Sb/Te of all the reaction phases remain as 2/3. The result indicates that Ni is the dominating diffusion species. The reaction results in the Co 0.2 Ni 0.8 /Sb 2 Te 3 couples are similar to those in the Ni/Sb 2 Te 3 couples. The reaction phase at 400°C is λ 2 -NiSb 1−x Te 2x , and are λ 1 -Ni(Sb 1−x Te x ) 1+y + Ni 5.66 SbTe 2 phases at 500°C with a longer reaction time. The compositional ratios of Sb/Te in the reaction phases are also 2/3, and the Co contents in the reaction phases are very limited. Ni is also the dominating diffusion species in the Co 0.2 Ni 0.8 /Sb 2 Te 3 couples. Graphical Abstract