Novel environmentally friendly blue pigments based on Li2Cu5(PO4)4

Novel environmentally friendly blue pigments, (Li1-xNax)(2)Cu-5(PO4)(4) (0 <= x <= 0.20), were synthesized and their color properties were investigated. By doping larger Na+ ions into Li+ ion sites, the crystal lattice was distorted, which strongly affected the d-d transition absorption nature of Cu2+. In the series of (Li1-xNax)(2)Cu-5(PO4)(4), (Li0.90Na0.10)(2)Cu-5(PO4)(4) showed a vivid blue hue with a blueness value (-b*) of 39.4 in the CIE L*a*b* system; this value is higher than that of the commercial Fe-4(III)[Fe-II(CN)(6)](3) pigment (dark blue, -b* = 19.3).

Automated summary

Novel environmentally friendly blue pigments were synthesized and their color properties were investigated. By doping different ions into the crystal lattice, a bright blue pigment with a higher blueness value than commercial pigments was obtained.