Synthesis and characterization of Zn1-xCoxO green pigments with low content cobalt oxide

A series of Zn1-xCoxO (x = 0.01, 0.02, 0.03 and 0.04) green pigments have been synthesized by solid-state reaction. The pigment samples were characterized by X-ray diffraction, scanning electron microscope, thermal gravimetric, differential scanning calorimetry, ultraviolet-visible diffuse reflectance spectroscopy and CIE L*a*b* colorimetric analysis. The results demonstrated that the synthetic pigment is a kind of new green hue based on crystal structure of zinc oxide, which can be used as color pigments. High energy ball milling (HEBM, the suitable milling time was 2 h) can reduce the particle size and make it uniform, also can improve the color properties of pigments. The calcination temperature of solid state reaction and the color brightness can be improved by adding 2 wt% CaF2. The appropriate calcination temperature for synthetic pigments is 1100 °C, and all samples remained the basic crystalline structure of ZnO. The content of cobalt oxide in the pigment is much less (about 1.8 wt%) than other cobalt based pigments. At the same time, the samples with milling showed better near infrared reflectance (NIR). Therefore, the prepared cobalt green pigment has a good application prospect.