Thermoelectrics are slabs of semiconductor with a strange and useful property: heating them on one side generates an electric voltage that can be used to drive a current and power devices. To obtain that voltage, thermoelectrics must be good electrical conductors but poor conductors of heat, which saps the effect. Unfortunately, because a material’s electrical and heat conductivity tend to go hand in hand, it has proven difficult to create materials that have high thermoelectric efficiency—a property scientists represent with the symbol ZT.
The key to the ultralow thermal conductivity, Kanatzidis says, appears to be the pleated arrangement of tin and selenium atoms in the material, which looks like an accordion. The pattern seems to help the atoms flex when hit by heat-transmitting vibrations called phonons, thus dampening SbSe’s ability to conduct heat. The researchers report the results today in Nature.