Towards more ecological ceramic pigments: Study of the influence of glass composition on the colour stability of a pink chromium-doped ceramic pigment

This paper describes the study of a pink ceramic pigment based on the optical properties of Cr-doped structures, having into account environmental considerations. The research is focused on the optimisation of the synthesis parameters in order to minimise the amount of pollutant Cr(VI) in the washing liquids and enhance chromatic coordinates. In a first stage, the Al2−xCrxO3 solid solution was studied. Nevertheless, the observation that ZnO was required in the frit to stabilise the pink colour after glazing made us to conduct the research towards the optimisation of the ZnAl2−xCrxO4 system. X-ray diffraction (XRD) indicates a solid solution formation based on the gahnite structure; moreover, no Cr(VI) and B contents were found in the analysis of the washing liquids. Thus, this research enabled us to produce a pink pigment with low environmental impact and good chromatic coordinates. Further study of the pigment applied in a glaze showed evidence of the importance of the glaze composition for the colour development and stability of the ceramic pigments.