Properties of Single Crystalline Semiconducting CoSb3

A study of the thermoelectric properties of the skutterudite compound CoSb3 was carried out on single crystals grown by the Bridgman gradient freeze technique. p- and n-type samples were obtained over a wide range of carrier concentration. Undoped As-grown crystals show p-type conductivity while n-type samples were obtained by addition of Te or Pd. Samples were characterized by x-ray diffractometry, electron microprobe analysis, and density measurements. The physical properties of CoSb3 such as linear thermal expansion coefficient, sound velocity, and Debye temperature were also determined and are presented. Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect measurements were performed between room temperature and about 900 K. Exceptionally high Hall mobilities were obtained on p-type samples with a maximum room-temperature Hall mobility of 3300 sq cm/V.s at a carrier concentration of 1 x 10(exp 17)/cc. The results of the transport property measurements are discussed and are in agreement with some recent predictions based on band structure calculations. The potential of CoSb3 for thermoelectric applications is evaluated.