Codoping Ti in low Co-containing hibonite achieving excellent optical properties for near-infrared reflective pigment applications

To reduce carcinogenic cobalt content in pigments, a series of near-infrared reflective pigments based on CaAl 12-x-y Co x Ti y O 19 (x = 0–0.5 and y = 0-(x+0.3)) were prepared via solid state reactions. Although the cobalt content in the pigment CaAl 11.7 Co 0.1 Ti 0.2 O 19 is only 0.87% by mass, the resulting pigment still has excellent color properties (64.89, 3.88, −40.30) and near-infrared reflectance (∼70%). The structural information of the obtained pigments were analyzed by XRD refinement, and the results revealed that the doping concentration of titanium relative to cobalt significantly affected the coordination structure of cobalt in hibonite, which in turn apparently influenced the optical properties of the obtained samples. The actual cooling effect of the CaAl 11.7 Co 0.1 Ti 0.2 O 19 coating was tested using a model house and the annual energy consumption was simulated by using EnergyPlus software. For a warm city (Haikou), using this CaAl 11.7 Co 0.1 Ti 0.2 O 19 coating can reduce energy consumption for cooling by 24.75%.