Chao-hong Wang

Interfacial Reactions in the Sn-Bi/Te Couples

Sn-Bi alloys are promising Pb-free solders and Te is the primary constituent element of the bismuth telluride thermoelectric materials. Interfacial reactions in the Sn-Bi/Te couples are examined herein. Very unusual cruciform patterns have been observed in the Sn-Bi/Te couples reacted at 250°C. The reaction product is the SnTe phase. The reaction layer thickness is very uniform along the Te substrate edges, and there are no reaction products at the substrate corners. The cruciform patterns of the reaction layers gradually disappear in the Sn-Bi/Te reaction couples with higher Bi contents, and the critical composition is about Sn-36.25at.%Bi (Sn-50wt.%Bi). The reaction product is also the SnTe phase in the Sn/Te couple reacted at 210°C but without the cruciform pattern. At 210°C, the SnTe phase layer in the Sn/Te couple has a duplex structure, and its growth rate follows a parabolic law.