Preparation and characterization of Mg2+-doped CaCu3Ti4O12 pigment with high NIR reflectance

Abstract A new inorganic pigment CaCu3-xMgxTi4O12 (x = 0.0, 0.2, 0.4, 0.6) with high reflectance at the near-infrared (NIR) band was synthesized by the traditional solid-phase method. The substitution of Mg2+ for Cu2+ in CaCu3Ti4O12 increased the band gap of pigments from 2.04 eV to 2.11 eV. This change was attributed to the charge transfer of O2p to Ti3d, which resulted in the color change of powder pigment samples from orange to yellow. The thermal performance of the corresponding pigmented coating was evaluated. Results showed that the NIR solar reflectance of the aluminum plate coated with CaCu3-xMgxTi4O12 (x = 0.0, 0.2, 0.4, 0.6) pigment reached as high as 48.5%–53.9%. CaCu2.6Mg0.4Ti4O12 was coated as a roof material of a building on the metal surface to determine differences in indoor temperature, and its thermal insulation effect was remarkable. Therefore, these CaCu3-xMgxTi4O12 powders have great potential in serving as cool pigments for building coatings.