Thermoelectric and Transport Properties of n-type Palladium-Doped Chalcopyrite Cu1−xPdxFeS2 Compounds

Semiconducting CuFeS 2 with a diamond-like structure has been recently studied as a potential candidate for thermoelectric applications. In the present study, Pd substitution for Cu was examined in terms of thermoelectric properties. A series of Pd-doped Cu 1− x Pd x FeS 2 ( x = 0–0.1) samples were synthesized. The thermoelectric and transport properties of hot-pressed sample pellets were characterized. We observed three effects: (1) Pd substituted for Cu behaves as an effective donor, increasing the free electron concentration. (2) Formation of the foreign phase—PdS—was observed above the solubility limit of Pd in CuFeS 2 ( x ≥ 0.02). (3) Segregation of the foreign phase is accompanied by the formation of Fe Cu 2 + antisite defects. All these effects synergically enhanced both the power factor S 2 ·σ and the thermoelectric parameter ZT. The highest values of the power factor (∼ 1 mW m −1 K −1 ) and the ZT parameter (∼ 0.19 at 573 K) were achieved in the Cu 0.9 Pd 0.1 FeS 2 sample.