ICT2014 Abstracts

Thermoelectric (TE) modules have a large potential for utilizing waste heat in the transport sector. For this potential is to be realized one requires both a high figure of merit (ZT)of the TE material and a reliable metallization technology. The metallization must fulfill several properties: good adhesion between the relevant layers to assure high electrical and thermal conductivity and mechanical integrity; minimimal diffusion of elements into and out of the TE material to prevent degradation of the properties of the TE module; and minimal thermo-mechanical stresses at both leg and module level to assure reliable operation. In this study the effect of different contact layer thicknesses, process temperatures and operations temperatures have been investigated. 

Finite element method (FEM) simulations were performed to calculate the thermo-mechanically induced stresses in a metallized skutterudite (CoSb₃) and magnesium silicide (Mg₂Si) thermoelectric leg. The stresses were calculated as a function of the contact layer thickness, ranging from 1 µm up to 100 µm. Two different contact layer materials were tested, nickel (Ni) and silver (Ag). The stresses were also calculated as a function of process temperature, i.e. the temperature at which the metallization was deposited (200 - 450 °C), and operating temperature (T_{hot side} : 400 – 550 °C, T_{cold side} : -20 – 100 °C). Finally, the residual stresses in the leg were calculated in off mode (T_{hot side} = T_{cold side} : -20 – 20 °C).

Keywords – Thermoelectricity, thermoelectric legs, metallization, thermo-mechanical stresses, finite element method (FEM)