Cheap as chips

Science 365, 495–498 (2019)

Thermoelectric materials convert an electric potential into a temperature difference, and so hold great promise for solid-state cooling devices that can be integrated into electronic devices, including computer chips. However, the current state-of-the-art materials for room-temperature applications — alloys based on Bi₂Te₃ — are expensive as they contain large amounts of tellurium. Jun Mao and collaborators have now demonstrated that a cheaper alloy of Mg₃Bi₂ has similar thermoelectric performance to Bi₂Te₃.

In its stoichiometric form, Mg₃Bi₂ is a semimetal with relatively poor thermoelectric performance because the contributions from holes and electrons partially cancel each other out. Doping with additional magnesium adds electrons to make the material n-type to counter this, and alloying with antimony increases the Seebeck coefficient by turning the material into a semiconductor. This produces a material with a thermoelectric figure of merit of approximately 0.9 at 350 K, only slightly smaller than the best Bi₂Te₃ alloys and at a fraction of the cost.