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)(2)Te-3 and n-type Bi-2(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)(2)Te-3 and Bi-2(Te,Se)(3). However, even though it is not an issue in the (Bi,Sb)(2)Te-3, the nickel diffuses several microns into the Bi-2(Te,Se)(3) during the soldering processing and degrades its performance. Diffusion coefficients of nickel in p-type (Bi,Sb)(2)Te-3 and in n-type Bi-2(Te,Se)(3) were also quantitatively studied. (C) 2008 American Institute of Physics.