GPHS-RTG or General Purpose Heat Source — Radioisotope Thermoelectric Generator, is a specific design of the Radioisotope Thermoelectric Generator (RTG) used on US space missions.
The MMRTG design incorporates PbTe/TAGS thermoelectric couples (from Teledyne Energy Systems).
However, as the magnitude of the Seebeck coefficient increases with phonon drag, it may be beneficial in a thermoelectric material for direct energy conversion applications.
The most important of these are the Francisco Pérez Ríos Thermoelectric plant and the PEMEX refinery as well as the Cruz Azul and Tolteca cement locations.