RARE EARTH PHOSPHATE COLLOIDAL DISPERSION AND PREPARATION METHOD.

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The invention concerns a rare earth colloidal dispersion and its preparation method. The dispersion is characterised in that it comprises anisotropic and disaggregated particle, or capable of being disaggregated, of at least a rare earth and a water-soluble monovalent acid anion having a pKa of at least 2.5. It is prepared by a method which consists in : mixing a solution of at least a rare earth salt with phosphate ions controlling the pH of the reaction medium at a value ranging between 4 and 9 and in the presence of a water-soluble monovalent acid having a pH of at least 2.5; optionally ripening the resulting mixture; separating the precipitate from the reaction medium : re-dispersing in water said precipitate.