Preparation of Co_xM_1-xAl₂O₄/kaolinite (M = Zn, Ca, and Mg) composite pigments for ceramic glaze

The high production cost of cobalt blue (CoAl₂O₄) pigments severely limits their wide application. Therefore, it is necessary to decrease the consumption of strategic cobalt resources to fabricate CoAl₂O₄ pigments with high blue intensity and good dispersion. Herein, Co_xM_1-xAl₂O₄/kaolinite (M = Zn, Ca, and Mg) composite pigments were prepared via coprecipitation followed by high-temperature crystallization using kaolinite and soluble metal salts as raw materials. It was revealed that the blue intensity of the composite pigments could be facilely adjusted by controlling the added amount and the type of the involved metal ions and the introduction of kaolinite. The incorporated metal ions could effectively change the cell parameters and further affect the electron transition of Co²⁺, while kaolinite provided a two-dimensional substrate to support the generated CoAl₂O₄ nanoparticles to improve the dispersion and reflective properties of visible light. Due to the synergistic effect of each component, the as-prepared composite pigments also exhibited satisfactory color properties and excellent thermal and suspension stability in ceramics. Therefore, this study was expected to develop a practical strategy for designing CoAl₂O₄ composite pigments with controllable blue intensity and low cobalt consumption for high-temperature ceramic glaze.