Formation and thermal stability of the skutterudite phase in films sputtered from Co20Sb80 targets

The formation process of the skutterudite phase in both binary and iron-doped films prepared from non-stoichiometric Co20Sb80 targets was investigated by means of DTA, XRD, and transport measurement techniques. The results of the measurements allowed us to determine the influence of iron incorporation on the thermal behavior of the Co–Sb-based skutterudite phase. The films prepared by a DC magnetron technique on substrates kept at room temperature were amorphous in the as-deposited state. The crystallization of the skutterudite structure was found to occur exothermally on heating at temperatures near 145 and 153 °C for iron-containing and binary films, respectively. Antimony as a secondary phase was established from XRD measurements after the crystalline structure formation. The transport properties, resistivity and thermopower, of the as-grown films are highly sensitive to the phase formation process. The temperature behavior of these properties during the first measuring cycle is in good agreement with DTA and XRD data showing that these techniques can be valuable instruments to investigate the phase formation. The transport properties as well as the lattice parameters of as-grown films exhibit a permanent modification during thermocycling. The films are sensitive to oxygen at elevated temperatures. Iron incorporation lowers the thermal stability of the films in air. The mechanisms of formation and stability of the skutterudite phase are discussed. [Copyright &y& Elsevier]