Synthesis and Characterization of Ca_1–xEu_xZrO₃ as Environmentally Friendly Inorganic Yellow Pigments

Abstract

Eu 2+ -doped calcium zirconates, Ca 1−x Eu x ZrO 3 (0 ≤ x ≤ 1), were synthesized as novel environmentally friendly inorganic yellow pigments by the conventional solid-state reaction method. The crystal structure, morphology, optical properties, and color were characterized. The Eu 2+ -doped samples strongly absorbed blue light in the wavelength range of 435−480 nm, which was caused by the 4f−5d allowed transition of Eu 2+ . The color of the sample gradually became brilliant yellow with increasing the Eu 2+ content. Among the samples synthesized in this study, the brightest yellow color was obtained with the Ca 0.7 Eu 0.3 ZrO 3 (a* = +11.5 and b* = +70.7) sample. Compared with the commercially available praseodymium yellow pigment (a* = −3.28, b* = +70.3), the yellowness value (b*) of Ca 0.7 Eu 0.3 ZrO 3 was comparable and the redness value (a*) was higher. As a result, this pigment exhibited a reddish yellow color as compared with praseodymium yellow. In addition, this pigment was chemically stable. Therefore, the Ca 0.7 Eu 0.3 ZrO 3 pigment has the potential to become a novel environmentally friendly inorganic yellow pigment.

Non-ammonolysis synthesis and characterisation of environmentally benign yellow pigments based on calcium–tantalum perovskite oxynitrides

“…47,49 The substitution of Ca 2+ with La 3+ induces changes in the Ta–O/N–Ta bond angles and this may contribute to the variations in the bandgap energies of Ca 1− x La x Ta(O,N) 3 . The colour coordinate data for CaTa(O,N) 3 and Ca 0.8 La 0.2 Ta(O,N) 3 prepared in this study were compared with those reported in the literature for CaTaO 2 N synthesised by ammonolysis 26 and conventional yellow pigments such as cadmium yellow, 25 BiVO 4 20 and ZrSiO 4 :Pr 20 (Fig. 10).…”

“…2) prepared by urea-nitriding method in this study. Data for CaTaO 2 N prepared via the ammonolysis method 26 and commercially available yellow pigments (CdS-ZnS (cadmium yellow), 25 BiVO 4 20 and ZrSiO 4 :Pr 20 ) are also displayed for comparison.…”

“…The development of alternatives that are applicable as environmentally-friendly yellow pigments is therefore strongly desired, and considerable efforts have been devoted to developing such alternative materials. [15][16][17][18][19][20][21][22][23][24] For example, praseodymium yellow (ZrSiO 4 :Pr) 21,22 and bismuth vanadate (BiVO 4 ) 23,24 have been developed as metal-oxide-based yellow pigments. However, the preparation of ZrSiO 4 :Pr is time consuming and its particles are poorly dispersible, which limits its use in paints and inks.…”

“…yellow pigments such as cadmium yellow,25 BiVO 420 and ZrSiO 4 :Pr20 (Fig.10). Although the yellowness (b*) value for CaTa(O,N) 3 prepared by using urea fell short of those for CaTaO 2 N prepared by ammonolysis and conventional yellow pigments, that for Ca 1Àx La x Ta(O,N) 3 was almost comparable to those of CaTaO 2 N obtained by ammonolysis and ZrSiO 4 :Pr.…”

“…10 CIE L*a*b* colour coordinate plots for Ca 1Àx La x Ta(O,N) 3 (x = 0, 0.2) prepared by urea-nitriding method in this study. Data for CaTaO 2 N prepared via the ammonolysis method26 and commercially available yellow pigments (CdS-ZnS (cadmium yellow),25 BiVO 420 and ZrSiO 4 :Pr 20 )…”