High thermoelectric conversion efficiency of MgAgSb-based material with hot-pressed contacts†
The efficiency of heat-to-electricity conversion based on the thermoelectric effect depends on the materials' nondimensional figure of merit zT. While recent years saw an increasing number of reports of large peak zT in thermoelectric materials, efficiency data are scarce. High conversion efficiency requires not only a large average zT in the operational temperature range, but also good electrical and thermal contacts to the material. In this work, we experimentally demonstrate a record high thermoelectric conversion efficiency of 8.5% with a single thermoelectric leg based on a recently reported p-type MgAgSb-based compound operating between 20 and 245 °C. The efficiency can exceed 10% by increasing the hot side temperature to 295 °C. The sample is fabricated with silver contact pads using a one-step hot-press technique eliminating a typically required sample metallization process. This significantly simplifies the fabrication of thermoelectric elements with low electrical and thermal contact resistances.