No abstract

The target of this study is to evaluate the suitability of a contact scheme designed for thermoelectric characterization of FeSi 2 -based materials with the combined thermoelectric measurement (CTEM) technique. A Fe 0.95 Co 0.05 Si 2 sample is mounted between the CTEM sample holder blocks made of molybdenum using Field's metal solder. The electrical contact resistance is monitored under thermal cycling up to 580 °C by an in-house built contact resistance in situ monitoring facility. After cycling, the microstructure was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy on the cross section of the contact zone. For the developed preparation process, the specific contact resistance was found suitably low up to 415 °C (<200 μΩ• cm 2 which is less than 10% of the sample resistance). Above 415 °C, oxidation degrades the electrical contact irreversibly.

The correlation of the electrical contact resistance measurement and microanalysis of the Field’s metal (FM)/Cr interface was used to determine the temperature-dependent reactions at the interface. Oxidation of Cr by oxygen contained in FM was identified through a sharp increase of the contact resistance around a certain temperature, above which the following resistance decrease was associated to a corrosion phase. The corrosion-oxidation turning point was evaluated around 390 °C. Cr saturation in FM combined with a complete consumption of the oxygen contained in the FM induced a stabilization of the interface giving a specific contact resistance of about 30 µΩ·cm2.