NIR reflective cobalt based pigment: pechini synthesis and optical characteristics

Cobalt chromite (CoCr2O4) is one of the commercially important CICPs which has intense bluish green color. Nano-sized CoCr2O4 with impressive near infrared (NIR) reflectance (R*=43%) was synthesized via Pechini method with the calcination temperature increasing from 900 to 1200 ºC. The developed nano-crystalline powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS) analysis, UV-vis-NIR diffuse reflectance spectroscopy and CIE-L*a*b* 1976 color scales. Results show that calcination temperature has strong effect on the crystallinity, morphology and optical properties of the pigments. The pigment prepared at 1200 ºC known as the optimum sample due to phase purity, homogenous morphology and higher reflectance properties.