Inorganic pigments and method for preparing same

Greenish-yellow, yellow and orange-yellow pigments with a dominant wave length comprised between 573 and 586 m.mu., said pigments being characterized in that they consist essentially of bismuth vanadate of monoclinic structure, bismuth phosphate of monoclinic structure and aluminum phosphate of orthorhombic structure and, in the case of yellow and orange-yellow pigments, also of a compound based on Bi.sub.2 O.sub.3 and V.sub.2 O.sub.5, the X-rays diffractogram of which shows the following peaks:

• 1.87, 1.88, 2.41, 2.77, 2.80, 3.11, 3.82 and 7.6 A;
• said pigments being further characterized in that they have a molar ratio Bi.sub.2 O.sub.3 /P.sub.2 O.sub.5 equal to 1 and a Bi.sub.2 O.sub.3 /V.sub.2 O.sub.5 molar ratio comprised between 1.39 and 5.59, while their molar ratio Al.sub.2 O.sub. /V.sub.2 O.sub.5 is different for the greenish-yellow pigments and for the yellow and orange-yellow pigments, and varies with the molar ratio Bi.sub.2 O.sub.3 /V.sub.2 O.sub.5 according to the following scheme:
• ______________________________________ Molar ratio Molar ratio Al.sub.2 O.sub.3 /V.sub.2 O.sub.5 Al.sub.2 O.sub.3 /V.sub.2 O.sub.5 of the of the Molar ratio greenish-yellow yellow and orange- Bi.sub.2 O.sub.3 /V.sub.2 O.sub.5 products yellow products ______________________________________ 5.59 1-3.1 >3.1-5.35 4.19 1-2.4 >2.4-4.0 3.35 1-2.1 >2.1-3.2 2.79 1-1.8 >1.8-2.7 2.39 1-1.6 >1.6-2.3 2.09 1-1.5 >1.5-2.0 1.86 1-1.4 >1.4-1.8 1.67 1-1.3 >1.3-1.6 1.52 1-1.2 >1.2-1.45 1.39 1-1.18 >1.18-1.35 ______________________________________