We have systematically investigated thermoelectric properties by a series of doping in layered cobaltites Bi2Sr2Co2Oy, verifying the contribution of narrow band. In particular, Sommerfeld coefficient is dependent on charge carriers’ density and as function of density of states (DOS) at Fermi level, which is responsible for the persistent enhancement of large thermoelectric power. Especially for Bi2Sr1.9Ca0.1Co2Oy, it may provide an excellent platform to be a promising candidate of thermoelectric materials. On the other hand, high‐performance thermoelectric materials require elaborate doping and synthesis procedures, particularly the essential thermoelectric mechanism still remains extremely challenging to resolve. In this chapter, we show evidence that thermoelectricity can be directly generated by a natural chalcopyrite mineral Cu1+xFe1−xS2 from a deep‐sea hydrothermal vent, wherein the resistivity displays an excellent semiconducting character, while the large thermoelectric power and high power factor emerge in the low x region where the electron‐magnon scattering and large effective mass manifest, indicative of the strong coupling between doped carriers and localized antiferromagnetic spins, adding a new dimension to realizing the charge dynamics. The present findings advance our understanding of basic behaviors of exotic states and demonstrate that low‐cost thermoelectric energy generation and electron/hole carrier modulation in naturally abundant materials is feasible.
Part of the book: Thermoelectrics for Power Generation