Using Metal-Carbon Eutectic Fixed Points for High Temperature Contact Thermometry at KRISS

The metal-carbon eutectic cells for calibrations of contact thermometers have been developed for high temperature contact thermometry at KRISS. The fabrication of the Fe-C, Co-C and Ni-C eutectic cells has been completed so far and their performance as secondary fixed-point cells has been tested. The experiments indicate that the melting plateaus of eutectic cells are more suitable as fixed points for their set-temperature dependence is weaker than that of the freezing plateau. Especially for the Fe-C eutectic system, the pre-freezing rate dependence of the melting plateau has been also investigated systematically. Our results point out that the slower pre-freezing results in a higher melting plateau. This result is consistent to the previous report and should be taken into account when the melting plateau of an Fe-C cell is used as a fixed point for the calibration of thermometers. Furthermore, a possible use of the Fe-C eutectoid transition as a fixed point is introduced