Novel green glaze based on Cr doped Bi4Si3O12 inorganic pigment: Synthesis, properties and characterizations

The novel green Bi 4- x Cr x Si 3 O 12 (0.1 ≤ x ≤ 0.4) pigments with near-infrared solar reflectance (R*%) of up to 82.75% were successfully synthesized by the solid-state method. All the XRD patterns are indexed with Bi 4 Si 3 O 12 (space group I -43 d ). Indicated by XPS analysis, the oxidation state of Cr in the as-prepared green pigment is +3. The green color is caused by the 4 A 2g → 4 T 1g ( 4 F) and 4 A 2g → 4 T 2g ( 4 F) transition of Cr 3+ based on the UV-Vis-NIR spectrum. The influence of pigment bandgap changes on coloration is elaborated through the calculation of the pigment's electronic structure. The novel green ceramic glaze was prepared by compounding 10   wt.% of the as-synthesized pigment with the glaze powder. The R*% of the glaze samples are all above 93%, proving that all the glaze samples have extremely high near-infrared reflection performance and great application potential. The macroscopic surface of the glaze is smooth and uniform. Using an optical microscope (with magnifications ranging from 50× to 1000×) to observe the removed glassy surface, no bubbles or cracks were found. The pigment particles are evenly and stably dispersed in the glaze. In the SEM test, it was found that there were closed bubbles with diameters around 20 μm in the glaze layer. Moreover, through X-CT scanning, the volume proportion of pores in the glaze sample was only 0.32%, which proved that the glaze has good density.