Synthesis and color properties of the CoAl2O4/Al2O3 hybrid blue pigments with low cobalt contents

The CoAl2O4/Al2O3 hybrid pigments with low cobalt content were prepared by heterogeneous chemical precipitation and calcination methods. The structure and properties of the synthesized pigments were characterized by XRD, SEM, EDX, UV–Vis spectroscopy and colorimetry. Results showed that the hybrid pigments were consisted of the CoAl2O4 spinel and Al2O3 corundum, and the CoAl2O4 spinel evenly covered on the surface of Al2O3 corundum. With the increasing Co/Al mole ratio, the CoAl2O4 spinel contents in the hybrid pigments increased, and the blue components (− b*) of the pigments were elevated. Comparing with pure CoAl2O4 pigments, the cobalt content of hybrid pigments was lower, but its blue components (− b*) were exceeded to 40 when the Co/Al mole ratio reached up to above 0.10, which was closed to that of the commercial cobalt blue pigments. The synthesized pigments presented good chemical and thermal stability, high tinting strength. The vivid blue PU paint and resin, blue glaze with low cobalt content were obtained by mixing 5 wt% CoAl2O4/Al2O3 hybrid pigments. Therefore, the hybrid pigments could be used as candidate to substitute for the expensive commercial cobalt blue pigments because of its lower cobalt content and brilliant blue hue.