Diffusion of nickel and tin in p-type (Bi,Sb)2Te3 and n-type Bi2(Te,Se)3 thermoelectric materials

The diffusion and spatial distribution of tin from solder, and nickel from diffusion barrier in p-type (Bi,Sb)2Te3 and n-type Bi2(Te,Se)3 thermoelectric materials were investigated using electron microscopy. The results indicate that nickel is a suitable diffusion-barrier material for tin in both (Bi,Sb)2Te3 and Bi2(Te,Se)3. However, even though it is not an issue in the (Bi,Sb)2Te3, the nickel diffuses several microns into the Bi2(Te,Se)3 during the soldering processing and degrades its performance. Diffusion coefficients of nickel in p-type (Bi,Sb)2Te3 and in n-type Bi2(Te,Se)3 were also quantitatively studied.