摘要
Background: Bi 2 Se 3 holds significant importance in thermoelectric applications, and Co is considered a promising candidate for use as a barrier layer. This study investigates the interfacial reactions between Co and Bi 2 Se 3 , along with the phase equilibria within the Bi-Co-Se system, to provide fundamental insights. Methods: The Bi-Co-Se alloys and Bi 2 Se 3 substrates were prepared with pure constituent elements. The Co/Bi 2 Se 3 couples were formed by electroplating Co onto the Bi 2 Se 3 substrates, followed by subjecting them to reactions at 400℃ and 500℃. Significant findings: Isothermal sections of the Bi-Co-Se phase equilibria at 400 °C and 500 °C have been proposed based on key ternary experimental results and phase diagrams of its three constituent binary systems. No ternary compounds were observed. The stable phases and phase relationships are similar at both 400℃ and 500℃, except for the instability of Co 9 Se 8 at 500℃. Significant interfacial reactions were observed in the Co/Bi 2 Se 3 couples reacted at 400℃ and 500℃. These results suggest that Co alone may not serve as a suitable barrier layer for Bi 2 Se 3 at temperatures exceeding 400 °C. The reaction path at 400℃ is Co/Co 1-ꭓ Se/(Bi 2 ) m (Bi 2 Se 3 ) n /Bi 2 Se 3 , with Se as the dominant diffusion species. Se atoms migrate towards Co to form the Co 1-ꭓ Se phase and leave a Se-depleted Bi 2 Se 3 behind to form (Bi 2 ) m (Bi 2 Se 3 ) n . Unexpected liquation occurred in the Co/B i2 Se 3 couple reacted at 500℃. This liquation resulted from the rapid outward diffusion of Se from the Bi 2 Se 3 , leading to the emergence of bismuth from the Se-depleted Bi 2 Se 3 and its transformation into a molten state.