Computational design of robust, compatible interconnect alloys for improved PbTe-based thermoelectric devices

Radioisotope power systems (RPSs) including thermoelectric systems are proven technologies for long-term power generation in distant, dark, and/or dusty environments where solar power is not viable. Despite significant advancements in thermoelectric (TE) material technology, modern TE systems rely on legacy TE technologies due to shortcomings in systems-integration and reliability of improved TE materials. Crucial TE material development challenges stem from the interface joining TE materials and the metallic interconnect (IC) material near the heater unit hot-end, which must be manufacturable, robust, and stable after decades of operation. In this program, QuesTek Innovations will leverage its Integrated Computational Materials Engineering (ICME) expertise and Materials by Designreg; technology to rapidly design and prototype a TE-IC junction combining a novel IC alloy design and a mechanically robust, highly efficient p-type PbTe material with improved power generation efficiency near radioisotope heater unit hot-end temperatures. Phase I involves thermodynamic database development and utilization of CALPHAD (CALculation of Phase Diagrams) methods to computationally design a junction between the PbTe material and a QuesTek-designed Co-based IC material with minimal experimental validation. Design will focus on thermodynamic interface stability and well-matched coefficients of thermal expansion between TE/IC materials to minimize thermal stress during fabrication and long-term operation. The database framework will be extended in Phase II work to design a similarly compatible IC-TE material junction for an improved n-type PbTe material, leading to further improved RPS efficiency. The longevity of a full device incorporating QuesTekrsquo;s novel IC alloy and improved p- and n-type PbTe materials will be simulated using CALPHAD-based diffusion simulations to capture performance over multiple decades and experimentally verified through long-term device stability tests.