TURNING HEAT INTO ELECTRICITY WITH HIGH-ENTROPY ENGINEERING

摘要

Thermoelectric devices, which use a temperature gradient to generate electricity, stand out most for their simplicity and dependability, making them ideal choices to power technologies like pacemakers and deep-space probes. However, their efficiency is still not competitive with other forms of power generation. An efficient thermoelectric device requires high electrical conductivity and low thermal conductivity, but these properties are interrelated by carrier concentration, so driving up electrical conductivity while preserving the necessary temperature gradient is impossible without a specialized approach. MnTe has emerged as a promising lead-free thermoelectric material, but its performance is limited by its low electrical conductivity. Now, Mercouri Kanatzidis and co-workers have transformed MnTe into a robust thermoelectric material using a technique known as high entropy engineering (DOI: 10.1021/jacs.lc07522). By alloying MnTe with AgSbTe_2, they produced a new semiconductor, AgMnSbTe_3, which adopts a NaCl rock salt structure with Ag, Mn, and Sb cations at the Na position. The mismatch in atomic radii of the randomly distributed cations induces distortion throughout the crystal. This distortion enhances scattering of heat-carrying phonons, which results in lower lattice thermal conductivity. Additionally, the unique electronic structure and presence of trace amounts of Ag_2Te at the boundaries of the AgMnSbTe_3 grains promotes hole transmission across the material, raising its electrical conductivity.