Bridgman-solution crystal growth and characterization of the skutterudite compounds CoSb3 and RhSb3

Compounds with the skutterudite structure have recently been identified as advanced thermoelectric materials. We report on the crystal growth and characterization of the skutterudite compounds CoSb3 and RhSb3 which form peritectically at 873 and 900 degrees C, respectively. Large single crystals were obtained by the vertical gradient freeze technique from solutions rich in antimony. The samples were characterized by high-temperature Hall-effect and electrical resistivity measurements. Bandgaps of 0.56 and 0.80 eV were estimated from these measurements for CoSb3 and RhSb3, respectively. N-type CoSb3 samples were obtained by doping with Te. Exceptionally high p-type Hall-mobility values have been measured and a room-temperature value of 3445 cm(2) V-1 s(-1) was obtained for CoSb3 at a carrier concentration of 4 x 10(17) cm(-3) and 8000 cm(2) V-1 s(-1) was obtained for RhSb3 at a carrier concentration of 3.5 x 10(18) cm(-3).