Enhancement of thermoelectric properties by atomic-scale percolation in digenite CuxS

Atomic-scale percolation phenomena of electric and thermal conductivity were found in digenite CuxS. Copper ions are randomly located between the closely packed sulphur ions and jump to another position via unoccupied interstices. Near the percolation threshold value (f(c) similar to 0.3) in the conductive region, a 60% enhancement of ZT value can be obtained. This indicates that the percolation phenomena can provide a new strategy to optimize the properties of thermoelectric materials, especially for quasi disordered materials.