Metal-carbon eutectic high temperature fixed points for in-situ calibration of radiation thermometers

The diffusivimeter of LNE has been modified by improving the inductive furnace used to heat the tested specimens in order to extend the operating temperature range up to 3000 �C. The temperature of specimen is one of the tricky parameters to be measured to ensure the relevance of the thermal diffusivity measurement and the associated uncertainty. At high temperature, radiation thermometers are used to determine the temperature of the specimens at which the thermal diffusivity measurements are performed. In addition to the periodic calibration of the radiation thermometers performed outside the experimental facility with black body sources, LNE proposes an in-situ verification method based on miniature high temperature fixed-point cells filled with metal-carbon eutectic alloys in order to detect and correct potential drift of the radiation thermometers between two out-of-process calibration operations. The proposed method enables high repeatable and reproducible temperature measurements on eutectic fixed-points (Pd-C, Pt-C and Ir-C) distributed in the range from 1500 �C to 2300 �C.