Development of High Temperature Thermoelectric Device Technologies to Validated Materials Performance and Reliability for Advanced ThermoElectric Couple (ATEC) Program

摘要

NASA has successfully demonstrated using Thermoelectric Radioisotope Generators (RTGs) as a power source to support a number of deep space missions. They have consistently demonstrated their extraordinary reliability and longevity (38 years of continuous operation for MHW-RTG on Voyager), relying on materials and device technologies developed in the 1960's and 1970's. The NASA Radioisotope Power Systems Program's Thermoelectric Technology Development Project (TTDP) is pursuing the development of more efficient thermoelectric technologies that can increase performance (conversion efficiency and specific power) by a factor of 2 to 4X over heritage systems. The TTDP's Advanced ThermoElectric Couple (ATEC) task has been advancing a new set of high performance materials and segmented device technologies that would offer a factor of 2 increase in conversion efficiency over Si-Ge alloys used in the GPHS-RTG. These materials, p-type Yb_(14)MnSb_n and n-type La_(3-x)Te_4 segmented with p- and n-type filled skutterudites, have demonstrated stable performance over two years of testing. Proof-of-principle segmented devices have achieved conversion efficiencies of up to 15% at beginning-of-life when tested in a vacuum environment at hot-junction temperature up to 1273K and a cold-junction temperature of 473K. ATEC is now focusing on developing high reliability, long life components and devices, including scale-up processing of materials with enhanced mechanical robustness, fabrication of metallized leg segments and chemically and mechanically stable hot side interfaces, as well as mechanically compliant segmented multi-couple device configurations. Such devices could enable the development of more capable RTGs, including modular system architectures.