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A3: High temperature materials
Skutterudites such as CoSb3 are compounds composed of group IX-B atoms (Co, Rh, and Ir) forming a simple cubic structure, and group V-A3 pnictide atoms (primarily Sb and As) forming rings inside 6 of every 8 cubes. P-type doping of CoSb3 has led to some advances in zT, but the p-type material remains less performing than the n-type material due to the fact that the valence band, dominated by Sb levels, has a low effective mass. One method for improving electronic properties is to introduce an effective resonant level into the energy levels occupied by the light hole band, thereby increasing the Seebeck coefficient without strongly effecting other transport properties. In previous work, Sn doping was tried in samples prepared by a spark plasma sintering method: this was developed to perform doping studies quickly at the cost of low electrical mobility. Here we analyze samples doped with Sn, Zn and other dopants substituting for Sb, but made by a much slower annealing method to optimize power factor. Samples are compared by thermopower, resistivity, and hole concentration.
Financial support for this investigation was provided by the U.S. Department of Energy (DOE)-U.S.–China Clean Energy Research Center (CERC-CVC) under the award No. DE-PI0000012