Design of diffusion barrier and buffer layers for β-Zn4Sb3 mid-temperature thermoelectric modules

Highlights: • We processed diffusion barrier and buffer layers for β-Zn₄Sb₃ thermoelectric module. • W-Ti diffusion barrier layer successfully blocked diffusion of Zn, Sb and Ag. • Ti buffer layer provided adhesion between W-Ti and its neighboring layers. • We used solid-liquid interdiffusion method to join the module with good bonding. • The module with Ti/W-Ti/Ti layers showed phase stability after high temperature aging. The purpose of this work was to investigate the feasibility of using sputtered Ti/W-Ti/Ti multilayer as diffusion barrier and buffer layers between β-Zn₄Sb₃ thermoelectric (TE) material and Ag interconnect layer for mid-temperature TE module applications. Interdiffusion at the interface was examined by both scanning electron microscope and Auger electron spectroscopy. After penetrating the Ti buffer layer, Ag, Zn and Sb were successfully blocked by the W-Ti diffusion barrier layer. We also proved that the TE sample with diffusion barrier and buffer layers showed phase stability after high temperature aging. Also, the sheet resistance decreased as the temperature increased and it indicated good electrical properties at high working temperatures. In addition, the solid-liquid interdiffusion method was used to join the TE module, and the bonding remained stable at the TE module working temperature.