In the ITS-90, the defining fixed point with the highest temperature is the copper point. Above this, no fixed point is available that can be widely used as a practical calibration device. High-temperature fixed points using metal-carbon eutectics may change this situation. Nine metal-carbon eutectics have melting temperatures in the range from the copper point to 2500°C, and melting plateaus have shown repeatability better than 70 mK. The eutectics can be held in graphite crucibles, which makes the cells practical devices for use in ultra-high temperature. The fixed points can benefit the future high temperature standards in various ways. They may play the role of transfer standards replacing standard lamps while extending the temperature range. The temperature scale may be realized with much smaller uncertainty by interpolation at a selected number of these fixed points. Extension of this technique to above 3000 K is also demonstrated with metal carbide-carbon eutectic.
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