LAUSR

Reproducibility of the tungsten carbide–carbon peritectic (WC–C) fixed point (3021 K) was investigated by comparing six WC–C blackbody-type cells with each other. All the cells were built at VNIIOFI and had the same design with a cell outer diameter of 24 mm and a cavity opening diameter of 3  mm. Four cells were built using tungsten powder supplied by Alfa Aesar, while the other two cells used powder from Zhuzhou KETE (China). The nominal purity of both suppliers was 99.999 %. All the cells were compared in the same furnace. A reference cell in the second furnace was used for monitoring the stability of a radiation thermometer. Melting temperatures (given by the point of inflection) of all six cells agreed within ±45 mK. The reproducibility, as a standard deviation of the measured temperatures, can be estimated as 35 mK. The Zhuzhou KETE cells showed a slightly lower temperature than the Alfa Aesar cells: by 32 mK on average, which is comparable with repeatability of the measurements.