Evolution of red ceramic pigments: from hazardous compounds to environmentally friendly alternatives

Synthesis of red ceramic pigments is a challenging task in the ceramic industry. Most classic reds are based on severely toxic materials including lead, arsenic, mercury, selenium, and cadmium, which are forbidden in many countries. On the other hand, the red color is super sensitive to the synthesis parameters, heat treatment conditions (atmosphere and temperature), particle size, etc. Therefore, achieving a bright true red shade and its stability at high temperatures is crucial. There has been a massive attempt to find a sustainable high-temperature resistant alternative for these hazardous compounds. Iron oxide is one of the first red pigments in history, but it cannot produce a bright red shade and its color is mostly red-brown. Ce2S3 is another red pigment with a beautiful red color. But it cannot stand the temperature above 350 °C in an oxidizing atmosphere. Doping lanthanides in the perovskites or entrapping the toxic beautiful chromophores in the core-shell structures are among the strategies to achieve safe bright red pigments. This review outlines the recent progress of hazardous classic reds to environmentally friendly ceramic red pigments. Various compounds and dopants, applied to develop sustainable reds, from simple iron-oxides to composites, solid solutions, core-shell structures, or even purified wastes have been covered in this review.