摘要
Background Bi2Te3 is the most frequently used thermoelectric compound, while Co exhibits promise as a barrier layer candidate. To provide fundamental information, the Bi-Co-Te phase equilibria isothermal sections at 500 and 400 ℃, as well as the Co/Bi2Te3 interfacial reactions at 500, 400, and 300 ℃, were determined.
Methods The Bi-Co-Te alloys and Bi2Te3 substrates were synthesized using high-purity constituent elements. To form the Co/Bi2Te3 couples, Co was electroplated onto the Bi2Te3 substrates, after which they were subjected to reactions at specific temperatures.
Significant findings In the Bi-Co-Te ternary system, no ternary compounds were found, and all the binary compounds have limited solubility for ternary elements. In the Co/Bi2Te3 couples, significant interfacial reactions were observed. The results suggest that Co alone is not a suitable barrier layer. The reaction paths are Co/CoTe/(Bi2)m(Bi2Te3)n/Bi2Te3 when reacted at 400 and 300 ℃. Although 500 ℃ is below the melting points of both Co and Bi2Te3, surprising liquation occurred, and the reaction path is Co/CoTe/Co+ (Bi2)m(Bi2Te3)n +liquid (I)/Bi2Te3 at 500 ℃. Based on the morphologies and results of the reaction path, it is concluded the dominating diffusion species is Te.