Thermoelectric materials are a useful tool in generating power from waste heat or transforming electric current into cooling power. Finding materials with large thermopower is vital for the development of thermoelectric generators and thermoelectric coolers. The effectiveness of a thermoelectric material for power applications is quantified by its thermoelectric figure of merit, ZT. In an insulator, thermopower is large, but since conductivity is low, ZT is characteristically low. Metals have robust conductivity yet lack strong thermopower so they yield relatively low ZT.