Abstract
The interfacial reactions between the Ni barrier layer and the popularly used P-type (Bi 0.25 Sb 0.75 ) 2 Te 3 and N-type Bi 2 (Te 0.9 Se 0.1 ) 3 thermoelectric substrates are examined at 300 °C and 250 °C. A NiTe 2 phase with significant Sb solubility, or a ternary compound, and a Bi-enriched (Bi, Sb) 2 Te 3 phase are formed in the Ni/(Bi 0.25 Sb 0.75 ) 2 Te 3 couples. Two phases, NiTe 2 and BiTe, are formed in the Ni/Bi 2 (Te 0.9 Se 0.1 ) 3 couples. Both of these two phases have significant ternary solubilities. The [Formula presented] and [Formula presented] phase diagrams at 300 °C are proposed based on very limited available phase diagrams of constituent binary and ternary systems. Their respective reaction paths in both couples are drawn on isothermal tetrahedrons. The average reaction rates in 10 days are 7 μm/day at 300 °C and 0.9 μm/day at 250 °C in the Ni/Bi 2 (Te 0.9 Se 0.1 ) 3 couples, and they are much faster compared to those in the Ni/(Bi 0.25 Sb 0.75 ) 2 Te 3 couples, which are 0.9 μm/day at 300 °C and 0.4 μm/h at 250 °C. It is concluded Te is the fastest diffusion species in both types of couples.