High stability tungsten strip lamps are no longer suitable comparison artefacts for high temperature radiation thermometry, because they are fragile, have a small target size, are restricted in temperature range and are not blackbodies. This study developed proof-of-concept high performance comparison artefacts, which overcome the problems encountered when using such lamps in comparisons of the International Temperature Scale of 1990 (ITS90) among National Metrology Institutes (NMIs). This work demonstrated the concept of using high temperature fixed points (HTFPs) that have unknown temperatures and hence suitable as blind comparison artefacts. Four of these novel HTFPs were designed, constructed, filled and measured in the work described here. Initially Co-C was chosen but due to robustness issues, Ni-C was the selected the base eutectic alloy. The Ni-C cells were doped in two different concentrations with selected elements in a successful attempt to change the pure eutectic transition temperature by some tenths of degrees Celsius. The realization temperatures of eutectic cells determined at Inmetro were compared to the ones predicted by thermochemical simulation, using Thermo-Calc software and thermochemical property databases. In addition they were used to perform a blind comparison with the National Physical Laboratory (UK), which did not know beforehand what their temperatures were. Very good results were achieved (scale agreement and cell stability), demonstrating that doped cells are very suitable high temperature comparison artefacts for radiation thermometry.