Large Thermoelectric Power Factor in Iron-Pnictide Derivatives

The iron-pnictide derivatives, superconductors when appropriately doped, present large thermoelectric power factors, with potential application for thermoelectric cooling at low temperatures. Various compounds of REFeAsO family (with RE = Sm, Nd or La, whether doped with fluorine or not) show large values of the Seebeck coefficient, typically of the order of -100 µV/K. A dependence of the Seebeck coefficient with the doping level was observed. The maximum values of the Seebeck coefficient are obtained at around 100 K with similar broad peak shapes independently of the three RE-ions we used.