Novel environmentally friendly inorganic red pigments based on calcium bismuth oxides

Abstract

Novel environmentally friendly inorganic red pigments based on calcium bismuth oxide, Ca3(Bi1−x RE x )8O15 (0 ⩽ x ⩽ 0.09; RE = Sc3+, Er3+, Y3+, Ho3+ and Dy3+), were successfully synthesized and the color properties were characterized. The color of these pigments depended on the composition and the synthesis condition, and the most vivid red color was obtained for the Ca3(Bi0.93Y0.07)8O15 sample calcined thrice at 800 °C for 2 h. The L* and a* values corresponding to brightness and red chromaticity for this pigment were 45.6 and +30.6, respectively, which were greater than those of a commercially available Fe2O3 pigment (L* = 38.4, a* = +29.5). Since the present pigment is composed of nontoxic and safe elements, it should be an attractive alternative to the conventional Fe2O3 pigment.