NOVEL RARE EARTH FLUOROSULFIDES OR OXYFLUOROSULFIDES, PROCESSES FOR THEIR PREPARATION AND THEIR USE AS COLORING PIGMENTS

摘要

The present invention relates to new rare earth fluorosulphides according to four embodiments, new rare earth oxyfluorosulphides, their preparation methods and their use as coloring pigment. The first mode fluorosulphide corresponds to the formula LnSF (Ln denotes a rare earth ) and has an average particle size of at most 5 m. That of the second mode is a mixed rare earth fluorosulfide of formula (Ln, Ln ') SF and in the form of a solid solution. The fluorosulfide of the third mode, according to a first variant, comprises at least one alkaline element and has a structure of LnSF type, the rare earth being chosen from yttrium and from the group ranging from lanthanum to erbium included. According to a second variant of this third mode, the fluorosulfide comprises at least one alkaline element, it has a hexagonal structure space group P63 22, the rare earth belonging to the group ranging from holmium to lutetium included including also yttrium . The fluorosulfide of the fourth mode corresponds to the formula Ln2 AF4 S2 in which A is an alkaline earth. The oxyfluorosulfide corresponds to the formula Ln3 S2 F3 O in which Ln represents at least one trivalent rare earth.