Structure and Thermoelectric Properties of Te- and Ge-Doped Skutterudites CoSb2.875-xGe0.125Tex

n-Type CoSb2.875-x Ge0.125Te (x) (x = 0.125 to 0.275) compounds with different Te contents have been synthesized by a melt-quench-anneal-spark plasma sintering method, and the effects of Te content on the structure and thermoelectric properties have been investigated. The results show that all specimens exhibited n-type conduction characteristics. The solubility limit of Te in CoSb2.875-x Ge0.125Te (x) is found to be x = 0.25. The solubility of Te in CoSb3 is increased through charge compensation of the element Ge. The room-temperature carrier concentration N (p) of CoSb2.875-x Ge0.125Te (x) skutterudites increases with increasing Te content, and the compounds possess high power factors. The maximum power factor of 3.89 x 10(-3) W m(-1) K-2 was obtained at 720 K for the CoSb2.625Ge0.125Te0.25 compound. The thermal conductivity decreases dramatically with increasing Te content due to strong point defect scattering. The maximum value of the thermoelectric figure of merit ZT = 1.03 was obtained at 800 K for CoSb2.625Ge0.125Te0.25, benefiting from a lower thermal conductivity and a higher power factor. The figure of merit is competitive with values reported for single-filled skutterudites.