New high-efficiency thermoelectric material achieved by cracking the crystal

Nature : Thermoelectric materials use heat to drive electrons through the material, serving as voltage sources for electronics. However, most such materials have only a 5-7% heat-to-electricity conversion efficiency. By altering one common thermoelectric material, lead telluride (PbTe), Mercouri Kanatzidis and a team at Northwestern University in Evanston, Illinois, were able to more than double the material’s efficiency. The chemists added sodium atoms to the PbTe’s ordered lattice structure to increase the electrical conductivity of the material, and they added another thermoelectric material to help maintain the temperature gradient. Then they introduced fractures to the crystal. The fractures allowed the electrons to move through the material but reflected the phonons (heat vibrations), slowing the spread of the heat. Kanatzidis believes that in two to three years, the technique will be improved to the point that a highly reactive chemical such as sodium will no longer be needed. But even with sodium, the new material is already good enough for some applications.