Temperature determination of the Si–SiC eutectic fixed point using thermocouples

The temperature of the Si–SiC eutectic fixed point for use in thermocouple thermometry has been determined. Three Si–SiC cells were fabricated from pure silicon powder within separate graphite crucibles. Each of the three cells was cycled through 17 melt–freeze cycles and subjected to temperatures above 1400 °C for a period of approximately 73 h, and none showed any sign of mechanical failure. The melting transition was measured using three types of thermocouple: one type S, one type B, and two Pt/Pd thermocouples calibrated at the fixed points of Ag, Cu, Fe–C, Co–C, and Pd (only for type B). The transition temperature, measured using the type S and two Pt/Pd thermocouples, was (1410.0 ± 0.8) °C with k = 2. However, the measurement uncertainty using the type B thermocouple was as large as 1.5 °C ( k = 2) due to the inhomogeneity of the thermocouple. The repeatability of the three Si–SiC cells was calculated to be 0.3 °C, and the extremes of the temperature measurement differed by 0.8 °C.