Coprecipitation synthesis of a green Co-doped wurtzite structure high near-infrared reflective pigments using ammonia as precipitant

A low content cobalt of green pigments have been synthesized by coprecipitation method. The pigments were characterized by XRD, SEM, TG-DSC, UV–vis and CIE L*a*b*C*h* colorimetric. The results show that the calcination temperature for the prepared pigments are only 1000 °C and all pigments maintain the basic ZnO crystal structure. The coprecipitation method and the ammonia as a precipitant can obtain fine and uniform particles, good colorimetric performance (a* = −17.25) and high near infrared reflectance value. Finally, the synthesized pigments were applied to the roof surface of a self-made experimental device for application testing, the results showed that the room temperature at which the roof was coated with the sample was nearly 10 °C lower than which the ordinary pigments were applied. So, the synthesized pigments have good thermal stability, chemical stability, high near infrared reflectance, and low cobalt nitrate content (1.92 wt%). Also, they are the excellent candidates for cool pigments.