Manufacturing and performances of silicide-based thermoelectric modules

Silicide-based materials are among the most promising candidates for a mass manufacturing of thermoelectric devices allowing converting waste heat into electricity in the medium temperature range (250–500 °C), as they are formed from abundant, low cost and non-toxic elements while exhibiting good thermoelectric properties. In order to manage the detrimental mismatch of thermal expansion coefficients between the n and p-type materials constituting the thermoelectric legs, inducing thus thermomechanical stresses, we propose in this paper a new design of modules having a 'half-skeleton' structure. Twenty-two modules consisting of two couples of thermoelectric legs combining n-type magnesium silicide Mg₂(Si, Sn) and p-type higher manganese silicide have been fabricated according to this design, the thermoelectric materials being manufactured by kilograms. It is clearly shown that all the interfaces present in the modules are free from cracks, oxygen, and diffusion. The remarkable repeatability of the measured thermoelectric performance attests the robustness of our manufacturing process. An average power output of 0.37 W has been achieved, i.e. a power density of 0.95 W/cm², for a temperature difference of 400 °C (hot side temperature of 450 °C), placing our modules at the state of the art level while using simple production tools and materials mass production. Comparing this performance to finite elements modelling, the performance could be even enhanced. Long term stability tests at a given temperature and under cycling conditions in different working atmospheres are underway.