Two Oxides Show Strong Thermoelectric Properties Despite Being Metallic

Thermoelectric materials convert temperature gradients to electric voltage and vice versa by causing charge carriers to diffuse from hot to cold parts of the material. They are used to power spacecraft, harness waste heat from sources including industrial plants and cars, generate electricity from solar heat, and provide low-cost cooling in consumer products. Good thermoelectric materials are normally semiconductors with implanted impurities, and their performance usually does not vary with the orientation of their crystal axes with respect to the temperature gradient.

Now, Khuong Ong and Ping Wu from the A*STAR Institute of High Performance Computing in Singapore and David J. Singh from Oak Ridge National Laboratory in the USA have uncovered two materials with previously unknown thermoelectric functionality1. The two materials are platinum cobalt oxide (PtCoO2) and paladium cobalt oxide (PdCoO2), both with a ‘delafossite’ structure (Fig. 1) more commonly associated with oxides of copper and iron. The compounds are unique for two reasons: they are metallic rather than semiconducting, and they show strong thermoelectric properties when their crystal axes are oriented in a particular way with respect to the temperature gradient.

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