Interfacial reactions in In/Bi2Se3, In/Bi2Te3 and In/Bi2(Se0.2Te0.8)3 couples

Bi-2(Se,Te)(3) is the most commonly used N-type thermoelectric materials. The interfacial reactions in In/ Bi2Se3 and In/Bi2Te3 couples at 400 degrees C, 250 degrees C and 200 degrees C and In/Bi-2(Se0.2Te0.8)(3) couples at 250 degrees C are systematically determined for the first time. Significant interfacial reactions are observed in all the couples. The reaction rate decreases when the reaction temperature is reduced and the reaction is fastest in the In/Bi2Te3 couple and slowest in the In/Bi2Se3 couple. After reaction for 5 minutes, the thickness of the reaction layer in the In/Bi2Te3 couple is 439 mu m, 44 mu m and 14 mu m at 400 degrees C, 250 degrees C and 200 degrees C, respectively. The reaction phases and reaction paths in these couples are determined. In the In/Bi-2(Se0.2Te0.8)(3) couple that is reacted at 250 degrees C, the reaction path is liquid(In)/In-4(Se,Te)(3)/liquid/(Bi-2)(m)(-Bi-2(Se,Te)(3))(n)/Bi-2(Se0.2Te0.8)(3). At 400 degrees C and 250 degrees C, Se and Te are the species that diffuse fastest in the reaction couples and the reaction path is primarily controlled by the speed with which Se and Te diffuse. However, the diffusion rates for Se and Te decrease significantly when the reaction temperature is reduced and at 200 degrees C, Se and Te cease to be the dominating diffusion species in the couples. (C) 2018 Elsevier B.V. All rights reserved.