Development of contacts for Mg2(Si,Sn)-based thermoelectric devices within a CALPHAD-based ICME framework

Kurzfassung

Mg (Si,Sn)-based/electrode contacts are crucial in the manufacturing of thermoelectric devices. The contact of dissimilar materials, of semiconducting and metallic type, is typically done using several contacting layers, e. g. solder fillers, diffusion barriers, which produce bonding layers by diffusionreaction in the interconnection zone (IZ). The multiphase/multilayered bonded region has intrinsic dissimilar physico-chemical properties; therefore, the IZ is susceptible to degradation and/or failure during long-term operation under a thermal gradient. A CALPHAD-based ICME approach using the ThermoCalc-Python framework is being used to simulate the diffusion-reaction phenomena at the IZ to identify expected bonding layers, thickness and morphology. Thermodynamic and kinetic calculations proved valuable for selection of optimal process conditions and potential contacting layers. Process conditions can be optimized to avoid undesired phases or to fine tune layer thicknesses and microstructure of desired phases. The interaction between the model parameters and the optimization as a whole largely profits from the ICME approach.