Thermoelectric Properties of Skutterudite CoSb3 Prepared by Arc Melting

The arc melting was employed to prepare undoped CoSb3 compounds and their thermoelectric properties were investigated. Specimen annealed at 400 degrees C for 24 hrs showed sound microstructure. However, considerable voids and cracks were found after annealing at above 500 degrees C. It seems to be attributed to the phase dissociation and thermal expansion due to phase transitions during annealing and cooling. Single phase delta-CoSb3 was successfully obtained by annealing at 400 degrees C for 24 hrs. In the case of increasing annealing temperature, phase decompositions occurred. Undoped CoSb3 showed p-type conduction and intrinsic semiconducting behavior at all temperatures examined. Thermoelectric properties were remarkably improved by annealing and they were closely related to phase transitions.