Ni-doped BaTi5O11: New brilliant yellow pigment with high NIR reflectance as solar reflective fillers

New brilliant yellow pigments of Ni-doped BaTi5O11 were synthesized via solid-state method. Pure monoclinic BaTi5O11 powders with high crystallinity were obtained when the calcination was performed at 1000 degrees C for 2 h. As-prepared pigments had particle size distribution that ranged from 0.5 to 2 mu m Ni2+ and Ni3+ ions coexisted in the lattice of BaTi5O11 host. Ni-doping resulted in reduced energy gap of 2.44 eV for Ni-doped BaTi5O11 from 3.08 eV for undoped BaTi5O11 because of valence band shift. BaTi5O11 pigments with 5% Ni exhibited excellent color performance (L = 95.1, a* = -9.12, b* = 65.12, C* = 65.75, and h degrees = 97.97) and impressive NIR reflectance of 76.19%. Approximately, 10.3 degrees C decrease in temperature was observed for inner surface of ceramic tiles coated with cool pigments relative to the temperature of ceramic tiles with blank PU coating.