| Abstract Scope |
Bi-Cu-Sn-Te is an important quaternary system. This study determined the liquidus projections and invariant reactions of the Bi-Cu-Sn-Te quaternary system, starting from those of its four constituent ternary systems. In the Bi-Sn-Te system, there are seven primary phases: (Sn), (Bi), (Te), SnTe, Bi2Te3, (Bi2)m(Bi2Te3)n, and a pseudo-solution, (SnTe)x(Bi2Te3)y. There are six invariant reactions. Among them, there is only one Class I reaction, L ↔️ Te + SnTe + (SnTe)x(Bi2Te3)y, at 394 ℃. In the Bi-Cu-Te system, there are eight primary phases: (Bi), (Cu), (Te), (CuTe), (Cu4Te3), (Cu2Te), (Bi2Te3) and (Bi2)m(Bi2Te3)n, with six invariant reactions. Among them, there is also only one Class I reaction, L ↔️ Te + Bi2Te3 + CuTe, at 332 ℃. The Bi-Cu-Sn system has miscibility gaps across large compositional ranges. Interesting microstructures are observed when alloys solidify pass through these miscibility gaps, and three types of morphology were observed: core-shell, stochastic droplet, and uniform dispersion. |