WC–C, Cr3C2–C and Mn7C3–C peritectic systems were investigated for their potential of serving as high-temperature reference points in thermometry. Mixtures of high-purity graphite powder with W, Cr and Mn powder of 99.99%, 99.9% and 99.95% purity by mass, respectively, were placed in graphite blackbody crucibles and melting/freezing plateaus were observed by means of a radiation thermometer. The observed melting temperatures were 2749 °C (WC–C), 1826 °C (Cr3C2–C) and 1331 °C (Mn7C3–C), with a repeatability—in each case—of 0.02 K. The melting range for WC–C and Cr3C2–C peritectics was roughly 0.1 K. WC–C showed a flat freezing plateau that agreed with the melting plateau within the repeatability. The three fixed points are possible candidates, like the metal (carbide)–carbon eutectic fixed points, in the realization of an improved high-temperature scale above the copper point.
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